SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

SCHEDULE 13E-3

TRANSACTION STATEMENT UNDER SECTION 13(e) OF THE

SECURITIES EXCHANGE ACT OF 1934 AND

RULE 13e-3 THEREUNDER

Rule 13e-3 Transaction Statement

Under Section 13(e) of the Securities Exchange Act of 1934

(Amendment No. ______)

AMERICAN MIDSTREAM PARTNERS, LP

(Name of Issuer)

American Midstream Partners, LP

Anchor Midstream Acquisition, LLC

Anchor Midstream Merger Sub, LLC

American Midstream GP, LLC

AMID GP Holdings, LLC

High Point Infrastructure Partners, LLC

Magnolia Infrastructure Partners, LLC

JP Energy Development, L.P.

Busbar II, LLC

Magnolia Infrastructure Holdings, LLC

ArcLight Energy Partners Fund V, L.P.

ArcLight PEF GP V, LLC

ArcLight Capital Holdings, LLC

ArcLight Capital Partners, LLC

Daniel R. Revers

(Names of Persons Filing Statement)

Common Units Representing Limited Partner Interests

(Title of Class of Securities)

02752P 100

(CUSIP Number of Class of Securities)

(Name, Address, and Telephone Numbers of Person Authorized to Receive Notices and Communications on Behalf of the Persons Filing Statement)

With copies to

This statement is filed in connection with (check the appropriate box):

Check the following box if the soliciting materials or information statement referred to in checking box (a) are preliminary copies: ☒

Check the following box if the filing is a final amendment reporting the results of the transaction: ☐

CALCULATION OF FILING FEE

INTRODUCTION

This Rule 13e-3 Transaction Statement on Schedule 13E-3 (this “Transaction Statement”), together with the exhibits hereto, is being filed with the Securities and Exchange Commission (the “SEC”) pursuant to Section 13(e) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), by: (i) American Midstream Partners, LP, a Delaware limited partnership (the “Partnership”) and the issuer of the common units representing limited partner interests in the Partnership (“Common Units”) that are subject to the Rule 13e-3 transaction; (ii) Anchor Midstream Acquisition, LLC, a Delaware limited liability company (“Parent”); (iii) Anchor Midstream Merger Sub, LLC, a Delaware limited liability company (“Merger Sub”); (iv) American Midstream GP, LLC, a Delaware limited liability company (“Partnership GP”); (v) AMID GP Holdings, LLC, a Delaware limited liability company; (vi) High Point Infrastructure Partners, LLC, a Delaware limited liability company (“HPIP”); (vii) Magnolia Infrastructure Partners, LLC, a Delaware limited liability company; (viii) JP Energy Development, L.P., a Delaware limited partnership; (ix) Busbar II, LLC, a Delaware limited liability company; (x) Magnolia Infrastructure Holdings, LLC, a Delaware limited liability company (“MIH”); (xi) ArcLight Energy Partners Fund V, L.P., a Delaware limited partnership; (xii) ArcLight PEF GP V, LLC, a Delaware limited liability company; (xiii) ArcLight Capital Holdings, LLC, a Delaware limited liability company; (xiv) ArcLight Capital Partners, LLC, a Delaware limited liability company; and (xv) Daniel R. Revers. Collectively, the persons filing this Transaction Statement are referred to as the “filing persons.”

This Transaction Statement relates to the Agreement and Plan of Merger, dated as of March 17, 2019 (the “Merger Agreement”), by and among the Partnership, Partnership GP, Parent, Merger Sub and HPIP. Pursuant to the Merger Agreement, Parent has agreed to acquire all of the publicly held equity (other than Common Units held by Parent or any Common Unit designated by Parent as a “Sponsor Unit” with the written consent of the holder of such Common Unit (collectively, the “Sponsor Units”)) in the Partnership under the terms of the Merger Agreement. Under the terms and subject to the conditions of the Merger Agreement, Merger Sub will merge with and into the Partnership, with the Partnership surviving as a wholly owned subsidiary of Parent and Partnership GP (the “Merger”), both of which are indirect controlled subsidiaries of ArcLight Energy Partners Fund V, L.P. The Merger will become effective upon the filing of a properly executed certificate of merger with the Secretary of State of the State of Delaware or at such later date and time as may be agreed by the parties and set forth in the certificate of merger (the “Effective Time”). The Merger Agreement provides that, at the Effective Time, each Common Unit issued and outstanding as of immediately prior to the Effective Time (other than the Sponsor Units) will be converted into the right to receive $5.25 in cash, to be paid without interest and reduced by any applicable tax withholding (the “Merger Consideration”). As of the Effective Time, all of the Common Units converted into the right to receive the Merger Consideration will no longer be outstanding and will automatically be canceled and cease to exist.

The Sponsor Units will be unaffected by the Merger and will remain outstanding, and no consideration will be delivered in respect thereof. The Partnership’s incentive distribution rights (“IDRs”) issued and outstanding immediately prior to the Effective Time will be automatically canceled and cease to exist, and no consideration shall be delivered in respect of the cancellation of the IDRs.

The closing of the Merger will occur on the third business day after the satisfaction or waiver of the conditions to the Merger provided in the Merger Agreement (other than the conditions that by their nature are to be satisfied at the closing of the Merger, but subject to the satisfaction or waiver of those conditions), or at such other date or time as the Partnership and Parent agree; provided, however, that without Parent’s written consent, the closing of the Merger may not occur prior to May 17, 2019.

The conflicts committee (the “Conflicts Committee”) of the board of directors of Partnership GP (the “GP Board”), consisting of three independent directors, has unanimously (i) determined that the Merger Agreement and the transactions contemplated thereby, including the Merger, are in the best interests of the Partnership and holders of Common Units other than Parent, Merger Sub, HPIP and their respective affiliates (the “Unaffiliated Unitholders”), (ii) granted “Special Approval,” as such term is defined in the Fifth Amended and Restated Agreement of Limited Partnership of the Partnership (as amended, the “Partnership Agreement”), of the Merger Agreement and the transactions contemplated thereby, including the Merger, and (iii) recommended that the GP Board adopt and approve the Merger Agreement and the consummation of the transactions contemplated thereby, including the Merger. In determining whether to make its recommendation, the Conflicts Committee considered,

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among other things, the opinion of Evercore Group, L.L.C. (“Evercore”), the financial advisor to the Conflicts Committee, to the effect that, as of the date of Evercore’s opinion, and based upon and subject to the assumptions made, procedures followed, matters considered, and qualifications and limitations of the review undertaken in rendering Evercore’s opinion as set forth therein, the Merger Consideration is fair, from a financial point of view, to the Unaffiliated Unitholders.

The GP Board, acting in part based upon the recommendation of the Conflicts Committee (and after receiving the approval of Partnership GP’s Class A members), has unanimously (i) determined that the Merger Agreement and the transactions contemplated thereby, including the Merger, are in the best interests of the Partnership, (ii) approved the Merger Agreement, the execution, delivery and performance of the Merger Agreement and the consummation of the transactions contemplated thereby, including the Merger, (iii) directed that the Merger Agreement and the transactions contemplated thereby, including the Merger, be submitted to a vote of the limited partners of the Partnership, and (iv) authorized the approval of the Merger Agreement and the transactions contemplated thereby, including the Merger, by the limited partners of the Partnership without a meeting, without a vote and without prior notice, pursuant to and on the conditions set forth in the Partnership Agreement.

Under the applicable provisions of the Partnership Agreement, approval of the Merger Agreement and the transactions contemplated thereby, including the Merger, requires the affirmative vote or consent of the holders of a majority of the outstanding Common Units and preferred units, voting together as a single class on an as-converted basis, and a majority of each series of the outstanding preferred units, voting separately as a class (collectively, a “Unit Majority” and, such approval, the “Partnership Unitholder Approval”). As permitted by the Delaware Revised Uniform Limited Partnership Act and the Partnership Agreement, immediately prior to the execution of the Merger Agreement, affiliates of Parent delivered to the Partnership a written consent of limited partners approving the Merger Agreement and the transactions contemplated thereby, including the Merger, by a Unit Majority, which consent constitutes the Partnership Unitholder Approval. Assuming the timely satisfaction or waiver of the conditions set forth in the Merger Agreement, the Partnership currently anticipates that the Merger will be completed in the second quarter of 2019.

Concurrently with the filing of this Transaction Statement, the Partnership is filing an information statement (the “Information Statement”) under Section 14(c) of the Exchange Act relating to the Merger Agreement and the transactions contemplated thereby, including the Merger. A copy of the Information Statement is attached hereto as Exhibit (a)(1). A copy of the Merger Agreement is attached as Annex A to the Information Statement. All references in this Transaction Statement to Items numbered 1001 to 1016 are references to Items contained in Regulation M-A under the Exchange Act.

Pursuant to General Instruction F to Schedule 13E-3, the information contained in the Information Statement, including all annexes thereto, is incorporated herein by reference in its entirety and responses to each item herein are qualified in their entirety by the information contained in the Information Statement and the annexes thereto. The cross-references below are being supplied pursuant to General Instruction G to Schedule 13E-3 and show the location in the Information Statement of the information required to be included in response to the items of Schedule 13E-3. As of the date hereof, the Information Statement is in preliminary form and is subject to completion. Terms used but not defined in this Transaction Statement have the meanings given to them in the Information Statement.

All information concerning the Partnership contained in, or incorporated by reference into, this Transaction Statement was supplied by the Partnership. Similarly, all information concerning any other filing person contained in, or incorporated by reference into, this Transaction Statement was supplied by such filing person.

Regulation M-A Item 1001

The information set forth in the Information Statement under the following captions is incorporated herein by reference:

“Summary Term Sheet”

“Questions and Answers about the Merger”

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Regulation M-A Item 1002

“Summary Term Sheet—Parties to the Merger Agreement”

“Summary Term Sheet—Action Approved by Written Consent of Unitholders Representing a Unit Majority”

“Unit Ownership of Certain Beneficial Owners and Management”

“Common Unit Market Price and Distribution Information—Common Unit Market Price Information”

“Common Unit Market Price and Distribution Information—Distribution Information”

“Information Concerning the Partnership—Prior Public Offerings”

Regulation M-A Item 1003

“Summary Term Sheet—Parties to the Merger”

“Information Concerning the ArcLight Filing Parties—Identity and Background of the ArcLight Filing Parties”

“Information Concerning the Partnership”

Regulation M-A Item 1004

“Summary Term Sheet”

“Questions and Answers about the Merger”

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“The Merger—Effects of the Merger”

“The Merger—Background of the Merger”

“The Merger—Recommendation of the Conflicts Committee and the GP Board; Reasons for Recommending Approval of the Merger”

“The Merger—Approval of the Merger”

“The Merger—Interests of the Directors and Executive Officers of Partnership GP in the Merger”

“The Merger—Position of the ArcLight Filing Parties as to the Fairness of the Merger”

“The Merger—Purpose and Reasons of the ArcLight Filing Parties for the Merger”

“The Merger—Primary Benefits and Detriments of the Merger”

“The Merger—Ownership of the Partnership After the Merger”

“The Merger—Financing of the Merger”

“The Merger—Provisions for Unaffiliated Unitholders”

“The Merger—No Appraisal Rights”

“The Merger—Ownership of the Partnership After the Merger”

“The Merger Agreement”

“Certain Purchases and Sales of Common Units”

“Material U.S. Federal Income Tax Consequences of the Merger”

Annex A: Merger Agreement

“Summary Term Sheet”

“Questions and Answers about the Merger”

“The Merger—Effects of the Merger”

“The Merger—Interests of the Directors and Executive Officers of Partnership GP in the Merger”

“The Merger—Financing of the Merger”

“The Merger—Provisions for Unaffiliated Unitholders”

“The Merger—No Appraisal Rights”

“The Merger Agreement”

Annex A: Merger Agreement

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“Summary Term Sheet—No Appraisal Rights”

“Questions and Answers about the Merger”

“The Merger—No Appraisal Rights”

“The Merger—Provisions for Unaffiliated Unitholders”

Regulation M-A Item 1005

“Summary Term Sheet”

“The Merger—Interests of the Directors and Executive Officers of Partnership GP in the Merger”

“Information Concerning the Partnership—About the Partnership”

“Information Concerning the ArcLight Filing Parties—Identity and Background of the ArcLight Filing Parties”

“Where You Can Find More Information”

Annex C: The Partnership’s Annual Report on Form 10-K for the Year Ended December 31, 2018

“Summary Term Sheet”

“The Merger—Effects of the Merger”

“The Merger—Background of the Merger”

“The Merger—Recommendation of the Conflicts Committee and the GP Board; Reasons for Recommending Approval of the Merger”

“The Merger—Financing of the Merger”

“The Merger—Interests of the Directors and Executive Officers of Partnership GP in the Merger”

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“The Merger—Position of the ArcLight Filing Parties as to the Fairness of the Merger”

“The Merger—Purpose and Reasons of the ArcLight Filing Parties for the Merger”

“The Merger Agreement”

“Past Contacts, Transactions and Negotiations”

Annex A: Merger Agreement

Annex C: The Partnership’s Annual Report on Form 10-K for the Year Ended December 31, 2018

“Summary Term Sheet”

“Questions and Answers about the Merger”

“The Merger—Effects of the Merger”

“The Merger—Interests of the Directors and Executive Officers of Partnership GP in the Merger”

“The Merger Agreement”

“Common Unit Market Price and Distribution Information”

“Where You Can Find More Information”

Annex A: Merger Agreement

Annex C: The Partnership’s Annual Report on Form 10-K for the Year Ended December 31, 2018

Regulation M-A Item 1006

“Summary Term Sheet”

“Questions and Answers about the Merger and the Special Meeting”

“The Merger—Effects of the Merger”

“The Merger—Financing of the Merger”

“The Merger—Primary Benefits and Detriments of the Merger”

“The Merger—Delisting and Deregistration of Common Units”

“The Merger—Interests of the Directors and Executive Officers of Partnership GP in the Merger”

“Delisting and Deregistration”

Annex A: Merger Agreement

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“Summary Term Sheet”

“Questions and Answers about the Merger”

“The Merger—Effects of the Merger”

“The Merger—Background of the Merger”

“The Merger—Recommendation of the Conflicts Committee and the GP Board; Reasons for Recommending Approval of the Merger”

“The Merger—Interests of the Directors and Executive Officers of Partnership GP in the Merger”

“The Merger—Position of the ArcLight Filing Parties as to the Fairness of the Merger”

“The Merger—Purpose and Reasons of the ArcLight Filing Parties for the Merger”

“The Merger—Primary Benefits and Detriments of the Merger”

“The Merger—Financing of the Merger”

“Delisting and Deregistration”

“The Merger Agreement”

Annex A: Merger Agreement

Regulation M-A Item 1013

“Summary Term Sheet”

“Questions and Answers about the Merger”

“The Merger—Effects of the Merger”

“The Merger—Background of the Merger”

“The Merger—Recommendation of the Conflicts Committee and the GP Board; Reasons for Recommending Approval of the Merger”

“The Merger—Position of the ArcLight Filing Parties as to the Fairness of the Merger”

“The Merger—Purpose and Reasons of the ArcLight Filing Parties for the Merger”

“The Merger—Interests of the Directors and Executive Officers of Partnership GP in the Merger”

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“Summary Term Sheet—No Solicitation by Partnership GP or the Partnership of Alternative Proposals”

“The Merger—Background of the Merger”

“The Merger—Recommendation of the Conflicts Committee and the GP Board; Reasons for Recommending Approval of the Merger”

“The Merger—Opinion of Financial Advisor to the Conflicts Committee”

“The Merger—BofA Merrill Lynch Financial Advisor Materials”

“The Merger—Position of the ArcLight Filing Parties as to the Fairness of the Merger”

“The Merger—Purpose and Reasons of the ArcLight Filing Parties for the Merger”

Annex B: Written Opinion of Evercore to the Conflicts Committee

“Summary Term Sheet”

“Questions and Answers About the Merger”

“The Merger—Effects of the Merger”

“The Merger—Background of the Merger”

“The Merger—Recommendation of the Conflicts Committee and the GP Board; Reasons for Recommending Approval of the Merger”

“The Merger—Opinion of Financial Advisor to the Conflicts Committee”

“The Merger— BofA Merrill Lynch Financial Advisor Materials”

“The Merger—Interests of the Directors and Executive Officers of Partnership GP in the Merger”

“The Merger—Position of the ArcLight Filing Parties as to the Fairness of the Merger”

“The Merger—Purpose and Reasons of the ArcLight Filing Parties for the Merger”

Annex B: Written Opinion of Evercore to the Conflicts Committee

“Summary Term Sheet”

“Questions and Answers about the Merger”

“The Merger—Effects of the Merger”

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“The Merger—Background of the Merger”

“The Merger—Recommendation of the Conflicts Committee and the GP Board; Reasons for Recommending Approval of the Merger”

“The Merger—Interests of the Directors and Executive Officers of Partnership GP in the Merger”

“The Merger—Position of the ArcLight Filing Parties as to the Fairness of the Merger”

“The Merger—Purpose and Reasons of the ArcLight Filing Parties for the Merger”

“The Merger—Financing of the Merger”

“The Merger—Primary Benefits and Detriments of the Merger”

“The Merger—Ownership of the Partnership After the Merger”

“The Merger—Delisting and Deregistration of Common Units”

“The Merger Agreement”

“Delisting and Deregistration”

“Material U.S. Federal Income Tax Consequences of the Merger”

Annex A: Merger Agreement

Regulation M-A Item 1014

The information set forth in the Information Statement under the following captions is incorporated herein by reference:

“Summary Term Sheet”

“The Merger—Background of the Merger”

“The Merger—Recommendation of the Conflicts Committee and the GP Board; Reasons for Recommending Approval of the Merger”

“The Merger—Opinion of Financial Advisor to the Conflicts Committee”

“The Merger— BofA Merrill Lynch Financial Advisor Materials”

“The Merger—Interests of the Directors and Executive Officers of Partnership GP in the Merger”

“The Merger—Position of the ArcLight Filing Parties as to the Fairness of the Merger”

“The Merger—Purpose and Reasons of the ArcLight Filing Parties for the Merger”

“The Merger Agreement”

Annex B: Written Opinion of Evercore to the Conflicts Committee

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“Summary Term Sheet—Action Approved by Written Consent of Unitholders Representing a Unit Majority”

“Questions and Answers about the Merger”

“The Merger—Recommendation of the Conflicts Committee and the GP Board; Reasons for Recommending Approval of the Merger”

“The Merger Agreement”

“Summary Term Sheet”

“The Merger—Effects of the Merger”

“The Merger—Background of the Merger”

“The Merger—Recommendation of the Conflicts Committee and the GP Board; Reasons for Recommending Approval of the Merger”

“The Merger—Opinion of Financial Advisor to the Conflicts Committee”

“The Merger—Interests of the Directors and Executive Officers of Partnership GP in the Merger”

“The Merger Agreement”

Annex B: Written Opinion of Evercore to the Conflicts Committee

“Summary Term Sheet”

“Questions and Answers about the Merger”

“The Merger—Background of the Merger”

“The Merger—Recommendation of the Conflicts Committee and the GP Board; Reasons for Recommending Approval of the Merger”

“The Merger—Position of the ArcLight Filing Parties as to the Fairness of the Merger”

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Regulation M-A Item 1015

The information set forth in the Information Statement under the following captions is incorporated herein by reference:

“Summary Term Sheet—Opinion of Financial Advisor to the Conflicts Committee”

“The Merger—Effects of the Merger”

“The Merger—Background of the Merger”

“The Merger—Opinion of Financial Advisor to the Conflicts Committee”

“The Merger— BofA Merrill Lynch Financial Advisor Materials”

“The Merger—Position of the ArcLight Filing Parties as to the Fairness of the Merger”

“The Merger—Purpose and Reasons of the ArcLight Filing Parties for the Merger”

“The Merger—Fees and Expenses”

“Where You Can Find More Information”

Annex B: Written Opinion of Evercore to the Conflicts Committee

The written opinion of Evercore is attached to the Information Statement as Annex B and is incorporated herein by reference.

Regulation M-A Item 1007

“Summary Term Sheet—Merger Consideration”

“Summary Term Sheet—Conditions to Consummation of the Merger”

“Summary Term Sheet—Fees and Expenses”

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“Summary Term Sheet—Financing of the Merger”

“The Merger—Background of the Merger”

“The Merger—Recommendation of the Conflicts Committee and the GP Board; Reasons for Recommending Approval of the Merger”

“The Merger—Interests of the Directors and Executive Officers of Partnership GP in the Merger”

“The Merger—Regulatory Approvals and Clearances Required for the Merger”

“The Merger—Financing of the Merger”

“The Merger—Fees and Expenses”

“The Merger Agreement”

“Summary Term Sheet—Fees and Expenses”

“The Merger—Financing of the Merger”

“The Merger—Fees and Expenses”

“The Merger Agreement—Expenses”

Regulation M-A Item 1008

“Summary Term Sheet—Parties to the Merger Agreement”

“Summary Term Sheet—The Merger”

“Summary Term Sheet—Treatment of Incentive Distribution Rights”

“The Merger—Effects of the Merger”

“The Merger—Interests of the Directors and Executive Officers of Partnership GP in the Merger”

“The Merger Agreement—The Merger”

“Certain Purchases and Sales of Common Units”

“Delisting and Deregistration”

“Unit Ownership of Certain Beneficial Owners and Management”

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Regulation M-A Item 1012

“Summary Term Sheet”

“Questions and Answers about the Merger”

“The Merger—Recommendation of the Conflicts Committee and the GP Board; Reasons for Recommending Approval of the Merger”

“The Merger—Interests of the Directors and Executive Officers of Partnership GP in the Merger”

“The Merger—Position of the ArcLight Filing Parties as to the Fairness of the Merger”

“The Merger—Purpose and Reasons of the ArcLight Filing Parties for the Merger”

“The Merger Agreement—Conditions to Consummation of the Merger”

“The Merger Agreement—Change in the GP Board Recommendation”

Regulation M-A Item 1010

“The Merger—Effects of the Merger”

“Selected Historical Consolidated Financial Data”

“Where You Can Find More Information”

Annex C: The Partnership’s Annual Report on Form 10-K for the Year Ended December 31, 2018

The Partnership’s Annual Report on Form 10-K for the year ended December 31, 2018 is incorporated herein by reference.

Regulation M-A Item 1009

“Summary Term Sheet”

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“Questions and Answers about the Merger”

“The Merger—Background of the Merger”

“The Merger—Recommendation of the Conflicts Committee and the GP Board; Reasons for Recommending Approval of the Merger”

“The Merger—Opinion of Financial Advisor to the Conflicts Committee”

“The Merger— BofA Merrill Lynch Financial Advisor Materials”

“The Merger—Interests of the Directors and Executive Officers of Partnership GP in the Merger”

“The Merger—Fees and Expenses”

Regulation M-A Item 1011

Regulation M-A Item 1016

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SIGNATURES

After due inquiry and to the best of each of the undersigned’s knowledge and belief, each of the undersigned certifies that the information set forth in this statement is true, complete and correct.

Dated as of April 24, 2019

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