EXHIBIT 3.1

[COMPLETE COMPOSITE COPY OF CERTIFICATE OF INCORPORATION AS AMENDED]

RESTATED CERTIFICATE OF INCORPORATION

ST. MARY LAND & EXPLORATON COMPANY

ST. MARY LAND & EXPLORATION COMPANY, a corporation organized and existing under and by virtue of the General Corporation Law of the State of Delaware, does hereby certify as follows:

1. The present name of the Corporation is St. Mary Land & Exploration Company. The name under which the Corporation was originally incorporated is St. Mary Parish Land Company. The date of filing the Corporation’s original Certificate of Incorporation with the Delaware Secretary of State was January 23, 1915.

2. This Restated Certificate of Incorporation merely restates and integrates and does not further amend the provisions of the Corporation’s Certificate of Incorporation, as it has been amended or supplemented, and there is no discrepancy between those provisions and the provisions of this Restated Certificate of Incorporation.

3. The Restated Certificate of Incorporation is herein set forth in full as follows:

FIRST: The name of this Corporation is ST. MARY LAND & EXPLORATION COMPANY.

SECOND: Its registered office in the State of Delaware is to be located in the City of Wilmington, County of New Castle. The agent in charge thereof is The Corporation Trust Company, Corporation Trust Center, 1209 Orange Street, Wilmington, Delaware 19801.

THIRD: The purpose of the Corporation is to engage in any lawful act or activities for which corporations may be organized under the General Corporation Law of the State of Delaware.

FOURTH: The total number of shares of capital stock which the Corporation shall have authority to issue is 200,000,000 shares, of $.01 par value each.

FIFTH: The existence of this Corporation is to be perpetual.

SIXTH: The private property of the stockholders shall not be subject to the payment of corporate debts to any extent whatever.

SEVENTH: The Directors shall have the power to adopt, amend or repeal the By-Laws, to fix reserves, and to authorize and cause to be executed, mortgages and liens, without limit as to the amount, upon the property and franchises of this Corporation.

EIGHTH: The Directors may, by resolution passed by a majority of the whole Board of Directors, designate one or more committees, each committee to consist of one or more of the Directors of the Corporation, who, to the extent provided in said resolution or in the By-Laws of the Corporation, shall have the power and authority of the Board of Directors in the management of the business and affairs of the Corporation and may have power to authorize the seal of the Corporation to be affixed to all papers which may require it.

NINTH: The Directors shall have authority to dispose, in any manner, of all or substantially all of the property of the Corporation, when as authorized by a resolution adopted by a majority of the outstanding capital stock of the Corporation.

TENTH: The By-Laws shall determine whether and to what extent the accounts and books of this Corporation, or any of them, shall be open to the inspection of the stockholders; and no stockholder shall have any right of inspecting any account, or book or document of this Corporation, except as conferred by law or the By-Laws, or by resolution adopted by a majority of the outstanding capital stock of the Corporation or by resolution of a majority of the whole Board of Directors.

ELEVENTH: The stockholders and Directors shall have power to hold their meetings and keep the books, documents and papers of the Corporation outside of the State of Delaware, at such places as may be from time to time designated by the By-Laws, except as otherwise required by the laws of Delaware.

TWELFTH: The Directors may exercise, in addition to the powers and authorities hereinbefore or by law conferred upon them, any such powers and authorities and may do all such acts and things as may be exercised or done by the Corporation, subject, nevertheless, to the provisions of law, and of this Certificate of Incorporation and of the By-Laws of the Corporation.

THIRTEENTH: No contract or transaction between the Corporation and one or more of its Directors or officers, or between the Corporation and any other corporation, partnership, association, or other organization in which one or more of its Directors or officers are directors or officers, or have a financial interest, shall be void or voidable solely for this reason, or solely because the Director or officer is present at or participates in the meeting of the Board of Directors or committee thereof which authorizes the contract or transaction, or solely because his or their votes are counted for such purpose, if: (a) the material facts as to his relationship or interest and as to the contract or transaction are disclosed or are known to the Board of Directors or the committee, and the Board of Directors or the committee in good faith authorizes the contract or transaction by the affirmative votes of a majority of the disinterested Directors, even though the disinterested Directors be less than a quorum, or (b) the material facts as to his relationship or interest and as to the contract or transaction are disclosed or are known to the stockholders entitled to vote thereon, and the contract or transaction is specifically approved in good faith by vote of the stockholders, or (c) the contract or transaction is fair as to the

Corporation as of the time it is authorized, approved or ratified by the Board of Directors, a committee thereof, or the stockholders. Common or interested Directors may be counted in determining the presence of a quorum at a meeting of the Board of Directors or of a committee which authorizes the contract or transaction.

FOURTEENTH: (a) The Corporation shall indemnify any person who was or is a party or is threatened to be made a party to any threatened, pending or completed action, suit or proceeding, whether civil, criminal, administrative or investigative (other than an action by or in the right of the Corporation) by reason of the fact that he is or was a Director, officer, employee or agent of the Corporation, or is or was serving at the request of the Corporation as a director, officer, employee or agent of another corporation, partnership, joint venture, trust or other enterprise, against expenses (including attorneys’ fees), judgments, fines and amounts paid in settlement actually and reasonably incurred by him in connection with such action, suit or proceeding if he acted in good faith and in a manner he reasonably believed to be in or not opposed to the best interests of the Corporation, and, with respect to any criminal action or proceeding, had no reasonable cause to believe his conduct was unlawful.

(b) The Corporation shall indemnify any person who was or is a party or is threatened to be made a party to any threatened, pending or completed action or suit by or in the right of the Corporation to procure a judgment in its favor by reason of the fact that he is or was a Director, officer, employee or agent of the Corporation, or is or was serving at the request of the Corporation as a director, officer, employee or agent of another corporation, partnership, joint venture, trust or other enterprise against expenses (including attorneys’ fees) actually and reasonably incurred by him in connection with the defense or settlement of such action or suit if he acted in good faith and in a manner he reasonably believed to be in or not opposed to the best interests of the Corporation and except that no indemnification shall be made in respect of any claim, issue or matter as to which such person shall have been adjudged to be liable for negligence or misconduct in the performance of his duty to the Corporation unless and only to the extent that the Court of Chancery of the State of Delaware or the court in which such action or suit was brought shall determine upon application that, despite the adjudication of liability but in view of all the circumstances of the case, such person is fairly and reasonably entitled to indemnity for such expenses which the Court of Chancery or such other court shall deem proper.

(c) To the extent that a Director, officer, employee or agent of the Corporation has been successful on the merits or otherwise in the defense of any action, suit or proceeding referred to in paragraphs (a) and (b) of this Article, or in defense of any claim, issue or matter therein, he shall be indemnified against expenses (including attorneys’ fees) actually and reasonably incurred by, him in connection therewith without the necessity of any action being taken by the Corporation other than a determination in good faith that such defense has been successful.

In all other cases, any indemnification under paragraphs (a) and (b) of this Article (unless ordered by a court) shall be made by the Corporation only as authorized in the specific case upon a determination that indemnification of the Director, officer, employee or agent is proper in the circumstances because he has met the applicable standard of conduct set forth in paragraphs (a) and (b) of this Article. Such determination shall be made

(1) by the Board of Directors by a majority vote of a quorum consisting of Directors who were not parties to such action, suit or proceeding, or (2) if such a quorum is not obtainable, or, even if obtainable if a quorum of disinterested Directors so directs, by independent legal counsel in a written opinion, or (3) by the stockholders.

(d) The termination of any, action, suit or proceeding by judgment, order, settlement, conviction or upon a plea of nolo contendere or its equivalent, shall not, of itself, create a presumption that the person seeking indemnification did not act in good faith and in a manner which he reasonably believed to be in or not opposed to the best interests of the Corporation, and, with respect to any criminal action or proceeding, had reasonable cause to believe that his conduct was unlawful. Entry of a judgment by consent as part of a settlement shall not be deemed a final adjudication of liability for negligence or misconduct in the performance of duty, or of any other issue or matter.

(e) Expenses incurred in defending a civil or criminal action, suit or proceeding may be paid by the Corporation in advance of the final disposition of such action, suit or proceeding as authorized by the Board of Directors in the specific case upon receipt of an undertaking by or on behalf of the Director, officer, employee or agent involved to repay such amount unless it shall ultimately be determined that he is entitled to be indemnified by the Corporation as authorized in this Article.

(f) The indemnification provided by this Article shall not be deemed exclusive of any other rights to which those seeking indemnification may be entitled under any by-law, agreement, vote of stockholders or disinterested Directors or otherwise, both as to action in his official capacity and as to action in another capacity while holding such office, and shall continue as to a person who has ceased to be a Director, officer, employee or agent and shall inure to the benefit of the heirs, executors and administrators of such a person.

(g) The Corporation may purchase and maintain insurance on behalf of any person who is or was a Director, officer, employee or agent of the Corporation, or is or was serving at the request of the Corporation as a director, officer, employee or agent of another corporation, partnership, joint venture, trust or other enterprise against any liability, asserted against him and incurred by him in any such capacity, or arising out of his status as such, whether or not the Corporation would have the power to indemnify him against such liability under the provisions of this Article.

(h) The provisions of this Article shall be separable and the invalidity of all or any part thereof as applied to any particular type of liability or any particular person shall not preclude application of any remaining portion thereof to such situation or such person, nor application of the provisions of this Article to any other situation or person.,

FIFTEENTH: (a) A Director of the Corporation shall not be personally liable to the Corporation or its stockholders for monetary damages for breach of fiduciary duty as a director, except that this Article FIFTEENTH shall not eliminate or limit a Director’s liability (i) for any breach of the Director’s duty of loyalty to the Corporation or its stockholders, (ii) for acts or omissions not in good faith or which involve intentional misconduct or a knowing violation of law, (iii) under Section 174 of the Delaware General Corporation Law

or (iv) for any transaction from which the Director derived an improper personal benefit. If the Delaware General Corporation Law is amended after approval by the stockholders of this Article FIFTEENTH to authorize corporate action further eliminating or limiting the personal liability of directors, then the liability of a Director of the Corporation shall be eliminated or limited to the fullest extent permitted by the Delaware Corporation Law, as so amended from time to time.

(b) Any repeal or modification of this Article FIFTEENTH shall not increase the personal liability of any Director of the Corporation for any act or occurrence taking place prior to such repeal or modification, or otherwise adversely affect any right or protection of a Director of the Corporation existing at the time of such repeal or modification.

(c) The provisions of this Article FIFTEENTH shall not be deemed to limit or preclude indemnification of a Director by the Corporation for any liability of a Director which has not been eliminated by the provisions of this Article FIFTEENTH.

SIXTEENTH: This Corporation reserves the right to amend, alter, change or repeal any provision contained in this Certificate of Incorporation, in the manner now or hereafter prescribed by the statutes of the State of Delaware, and all rights conferred on officers, Directors and stockholders herein are granted, subject to this reservation.

4. This Restated Certificate of Incorporation was duly adopted by the Board of Directors of the Corporation in accordance with the applicable provisions of Section 245 and has been executed in accordance with Section 103 of the General Corporation Law of the State of Delaware.