Exhibit 4.1

EXECUTION VERSION

ASSIGNMENT AND ASSUMPTION AGREEMENT

THIS ASSIGNMENT AND ASSUMPTION AGREEMENT (this “Agreement”) is made as of February 5, 2020, by SEASPAN CORPORATION, a corporation duly organized and existing under the laws of the Marshall Islands (the “Existing Parent Company”), each of the undersigned GUARANTORS party hereto, ATLAS CORP., a corporation duly organized and existing under the laws of the Marshall Islands (the “New Parent Company”) and each of the undersigned INVESTORS party hereto (each an “Investor” and collectively, the “Investors”).

W I T N E S S E T H:

WHEREAS, pursuant to a Permitted Reorganization (as defined in a thirteenth supplemental indenture, dated as of January 13, 2020, among Seaspan Corporation, the guarantors party thereto and The Bank of New York Mellon (the “Thirteenth Supplemental Indenture”)), Seaspan Corporation, through a series of transactions, will become a direct wholly-owned subsidiary of the New Parent Company.

WHEREAS, prior to the consummation of the Permitted Reorganization, the Existing Parent Corporation is party to, among others, the following agreements:

(a) a subscription agreement, dated as of January 17, 2018, among Seaspan Corporation and each of the other undersigned parties thereto (as amended, the “January 2018 Subscription Agreement”);

(b) a registration rights agreement, dated as of February 14, 2018, among Seaspan Corporation and the investors specified therein (as amended, the “February 2018 Registration Rights Agreement”);

(c) a subscription agreement, dated as of March 13, 2018, among Seaspan Corporation and each of the other undersigned parties thereto (as amended, the “March 2018 Subscription Agreement”);

(d) an omnibus agreement, dated May 31, 2018, among Seaspan Corporation and each of the other undersigned parties thereto (the “Omnibus Agreement”);

(e) a warrant agreement, dated as of July 16, 2018, among Seaspan Corporation, Wentworth Insurance Company Ltd. and Hamblin Watsa Investment Counsel Ltd. (as amended, the “July 2018 Warrant Agreement”);

(f) a registration rights agreement, dated as of July 16, 2018, among Seaspan Corporation and the investors specified therein (the “July 2018 Registration Rights Agreement”); and

(g) a registration rights agreement, dated as of January 15, 2019, among Seaspan Corporation and the investors specified therein (as amended, the “January 2019 Registration Rights Agreement” and, together with the February 2018 Registration Rights Agreement and the July 2018 Registration Rights Agreement, the “Registration Rights Agreements”).

The “Specified Agreements” means the January 2018 Subscription Agreement, the February 2018 Registration Rights Agreement, the March 2018 Subscription Agreement, the Omnibus Agreement, the July 2018 Warrant Agreement, the July 2018 Registration Rights Agreement and the January 2019 Registration Rights Agreements.

WHEREAS, the Existing Parent Company has advised the Investors that, contemporaneously with the Permitted Reorganization, Seaspan Corporation will assign the Specified Agreements to the New Parent Company and the New Parent Company will assume the Specified Agreements, including, without limitation, any rights and obligations of the Existing Parent Company in each of the Specified Agreements.

WHEREAS, each of the Investors consents to (i) the Existing Parent Company’s assignment of the Specified Agreements to the New Parent Company and (ii) the New Parent Company’s assumption of the Specified Agreements.

WHEREAS, the parties to this Agreement agree, as of the date hereof, to amend the requirement to maintain the listing of the Registrable Debt Securities (as defined in each of the February 2018 Registration Rights Agreement and the January 2019 Registration Rights Agreement) on the New York Stock Exchange to allow the Existing Parent Company to list such Registrable Debt Securities on the Global Exchange Market, or another national exchange as may be mutually agreed by the parties from time to time.

NOW, THEREFORE, for good and valuable consideration, the sufficiency and receipt of which are hereby acknowledged, the parties hereto, intending to be legally bound, hereby agree as follows:

1. Assignment. Subject to Sections 3, 5 and 6 hereof, the Existing Parent Company hereby assigns its rights and obligations under each of the Specified Agreements to the New Parent Company, in the same manner and with the same force and effect as if the New Parent Company had been specifically named in the Specified Agreements, without the necessity for the execution by the Existing Parent Company of any other documents in addition to this Agreement. The foregoing assignment by the Existing Parent Company shall be absolute and unconditional, and such assignment shall not be subject to any defenses, waivers, claims or offsets to the extent any may exist. Notwithstanding the foregoing, this Agreement shall not constitute an assignment of any rights or obligations of the Investors under the Specified Agreements relating to the indenture, dated as of October 10, 2017 (the “Base Indenture”), providing for the issuance by the Existing Parent Company from time to time of its securities to be issued in one or more series, which Base Indenture was amended and supplemented by (i) a second supplemental indenture, dated as of February 14, 2018 (the “Second Supplemental Indenture”), among the Existing Parent Company, the guarantors party thereto and The Bank of New York Mellon, as trustee (the “Trustee”), providing for the issuance of a series of securities designated as its “5.50% Senior Notes due 2025”, in an aggregate principal amount of $250,000,000 (the “2025 Notes”), (ii) a third supplemental indenture, dated as of February 22, 2018 (the “Third Supplemental Indenture”), among the Existing Parent Company, the

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guarantors party thereto and the Trustee, (iii) a fourth supplemental indenture, dated as of March 22, 2018 (the “Fourth Supplemental Indenture”), among the Existing Parent Company, the guarantors party thereto and the Trustee, (iv) a fifth supplemental indenture, dated as of March 26, 2018 (the “Fifth Supplemental Indenture”), among the Existing Parent Company, the guarantors party thereto and the Trustee, (v) a sixth supplemental indenture, dated as of March 26, 2018 (the “Sixth Supplemental Indenture”), among the Existing Parent Company, the guarantors party thereto and the Trustee, (vi) a seventh supplemental indenture, dated as of June 8, 2018 (the “Seventh Supplemental Indenture”), among the Existing Parent Company, the guarantors party thereto and the Trustee, (vii) an eighth supplemental indenture, dated as of July 16, 2018 (the “Eighth Supplemental Indenture”), among the Existing Parent Company, the guarantors party thereto and the Trustee, (viii) a ninth supplemental indenture, dated as of January 15, 2019 (the “Ninth Supplemental Indenture”), among the Existing Parent Company, the Guarantors and the Trustee, providing for the issuance of a series of securities designated as its “5.50% Senior Notes due 2026”, in an aggregate principal amount of $250,000,000 (the “2026 Notes” and, together with the 2025 Notes, the “Notes”), (ix) a tenth supplemental indenture, dated as of January 15, 2019 (the “Tenth Supplemental Indenture”), among the Existing Parent Company, the guarantors party thereto and the Trustee, (x) an eleventh supplemental indenture, dated as of August 22, 2019 (the “Eleventh Supplemental Indenture”), among the Existing Parent Company, the guarantors party thereto and the Trustee, (xi) a twelfth supplemental indenture, dated as of August 22, 2019 (the “Twelfth Supplemental Indenture”), among the Existing Parent Company, the guarantors party thereto and the Trustee, and (xii) the Thirteenth Supplemental Indenture. The Base Indenture, the Second Supplemental Indenture, the Third Supplemental Indenture, the Fourth Supplemental Indenture, the Fifth Supplemental Indenture, the Sixth Supplemental Indenture, the Seventh Supplemental Indenture, the Eighth Supplemental Indenture, the Tenth Supplemental Indenture, the Eleventh Supplemental Indenture and Thirteenth Supplemental Indenture are referred to collectively as the “2025 Notes Indenture”. The Base Indenture, the Ninth Supplemental Indenture and the Thirteenth Supplemental Indenture are referred to collectively as the “2026 Notes Indenture” (together with the 2025 Notes, the 2025 Notes Indenture and the 2026 Notes, the “Fairfax Notes and Indentures”.

2. Assumption. Subject to Sections 3, 5 and 6 hereof, the New Parent Company hereby undertakes, accepts and assumes the assignment of each of the Specified Agreements and assumes all rights and obligations of the Existing Parent Company under each of the Specified Agreements and covenants to perform and discharge the same in the same manner and with the same force and effect as if the New Parent Company had been specifically named in the Specified Agreements, without the necessity for the execution by the New Parent Company of any other documents in addition to this Agreement. The foregoing assumption by the New Parent Company shall be absolute and unconditional, and such assumption shall not be subject to any defenses, waivers, claims or offsets to the extent any may exist. The New Parent Company expressly agrees that it has read and approved of, and will comply with and be bound by all of the relevant terms and conditions contained in, the Specified Agreements to which it will be a party after giving effect to this Agreement. Notwithstanding the foregoing, this Agreement shall not constitute an assumption of any rights or obligations of the Investors under the Specified Agreements relating to the Fairfax Notes and Indentures. From and after the effectiveness of this Agreement, pursuant to Section 6 hereof, all references to the Existing Parent Company in each of the Specified Agreements shall be deemed to be to the New Parent Company, except to the extent such references related to the Fairfax Notes and Indentures.

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3. Consent and Release; Effect on Warrants. Each Investor hereby consents to the assignment and assumption of each of the Specified Agreements, as set forth in Section 1 and 2 above. The parties hereto agree that the Specified Agreements will remain in full force and effect after giving effect to this Agreement. Each Investor, upon the effectiveness of this Agreement pursuant to Section 6 hereof, hereby releases the Existing Parent Company from all its duties and obligations with respect to the Specified Agreements other than (i) any liabilities in respect of any breach occurring prior to the date of such release and (ii) obligations in relation to the Fairfax Notes and Indentures. The parties hereby acknowledge and agree that from and after the assignment and assumption contemplated hereby, references to the “Company” shall be deemed to be references to New Parent Company and references to “Common Stock” shall be deemed to be references to common shares of New Parent Company, such that by its terms, from and after the assignment and assumption contemplated hereby, the July 2018 Warrant Agreement shall apply with respect to common shares of New Parent Company on the same terms and conditions, and shall be exercisable for the same number of common shares of the New Parent Company.

4. Successors and Assigns. All covenants and other agreements contained in this Agreement by or on behalf of any of the parties hereto bind and inure to the benefit of their respective successors and assigns (including any subsequent holder of the Notes (as defined in the Thirteenth Supplemental Indenture), the Warrants (as defined in the July 2018 Warrant Agreement) and the Registrable Shares (as defined in each of the Registration Rights Agreements)), whether so expressed or not. Nothing in this Agreement, expressed or implied, shall be construed to confer upon any person (other than the parties hereto and their respective successors and assigns permitted hereby) any legal or equitable right, remedy or claim under or by reason of this Agreement.

5. Effect on Registration Rights Agreements; Amendment. The parties acknowledge and agree that in connection with the assignment and assumption of the Registration Rights Agreements contemplated hereby, the provisions of the Registration Rights Agreements that relate to the Warrant Agreements (each as defined in the relevant Registration Rights Agreement), and to common shares issuable upon exercise of the warrants issued under the Warrant Agreements (or to common shares previously issued as a result of the exercise of warrants), are hereby amended so that all references to the Company are deemed to be references to New Parent Company, such that, for example, the obligation to prepare and file a resale registration statement with respect to common shares issuable upon exercise of the warrants issued under the Warrant Agreements shall be deemed to be references to resale registration statements to be prepared, filed and maintained by New Parent Company with respect to common shares of New Parent Company issued upon exercise of warrants. In addition, the last sentence in each of Section 2.5 of the February 2018 Registration Rights Agreement and Section 2.5 of the January 2019 Registration Rights Agreement shall be deleted in its entirety and replaced, in each case, with the following sentence:

“Following the initial listing of the Registrable Securities, the Company shall use its best efforts to:

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(i) maintain the listing of the Registrable Shares for so long as Company’s Common Stock continues to be listed on the NYSE or, if the Common Stock is not then listed on the NYSE, on the primary national securities exchange or automated quotation system on which the Common Stock is then listed or authorized for quotation or on any over-the-counter market; and

(ii) list the Registrable Debt Securities on the Global Exchange Market, or another national exchange as may be mutually agreed by the parties from time to time, and maintain such listing until such Registrable Debt Securities are no longer outstanding.”

6. Effectiveness. This Agreement shall become effective upon the consummation of the Permitted Reorganization; provided that, Section 5 of this Agreement shall become effective as of the date hereof.

7. Governing Law. This Agreement shall be governed and construed in accordance with the laws of the State of New York applicable to agreements made or instruments entered into and, in each case, performed in the State of New York. Any dispute, action or proceeding arising out of or relating to this Agreement in respect hereof or the rights of any party under this Agreement shall be exclusively maintained in the U.S. federal or New York State Court sitting in the Borough of Manhattan, The City of New York, New York. Each of the parties hereto: (i) agrees that a final judgment in any such action or proceeding shall be conclusive and may be enforced in other jurisdictions by suit on the judgment or in any other manner provided by law, and (ii) irrevocably submits to the jurisdiction of such courts in any suit, action or proceeding. Each party to this Agreement irrevocably waives, to the fullest extent permitted by applicable law, all right of trial by jury in any action, proceeding or counterclaim based on, or arising out of, under or in connection with this Agreement or any matter arising hereunder.

8. Counterparts. This Agreement may be executed in any number of counterparts, each of which shall be an original but all of which together shall constitute one instrument. Each counterpart may consist of a number of copies hereof, each signed by less than all, but together signed by all, of the parties hereto. Delivery of an executed signature page by facsimile, e-mail or electronic (e.g. “.pdf”’ or “.tif”) transmission shall be effective as delivery of a manually signed counterpart of this Agreement.

9. Severability. Any provision of this Agreement that is prohibited or unenforceable in any jurisdiction shall, as to such jurisdiction, be ineffective to the extent of such prohibition or unenforceability without invalidating the remaining provisions hereof, and any such prohibition or unenforceability in any jurisdiction shall (to the full extent permitted by law) not invalidate or render unenforceable such provision in any other jurisdiction.

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IN WITNESS WHEREOF, the parties have caused this Agreement to be duly executed as of the date first above written.