3 1 h84352e3.txt USX CORPORATION FOR PENNACO ENERGY, INC. 1 -------------------------- OMB APPROVAL -------------------------- -------- OMB Number: 3235-0104 FORM 3 Expires: December 31, 2001 -------- Estimated average burden hours per response.... 0.5 -------------------------- UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(f) of the Investment Company Act of 1940 ----------------------------------------------------------------------------------------------------------------------------------- 1. Name and Address of Reporting Person* 2. Date of Event Requiring 4. Issuer Name and Ticker or 6. If Amendment, Date Statement Trading Symbol of Original USX Corporation (Month/Day/Year) Pennaco Energy, Inc. (PN) (Month/Day/Year) ---------------------------------------- ------------------------------------ (Last) (First) (Middle) 02/06/01 5. Relationship of Reporting ----------------------- 600 Grant Street ---------------------------- Person(s) to Issuer 7. Individual or Joint/ ---------------------------------------- 3. I.R.S. Identification (Check all applicable) Group Filing (Check (Street) Number of Reporting Director X 10% Owner Applicable Line) Person, if an entity ----- ----- Form filed by Pittsburgh PA 15219-4776 (voluntary) Officer Other (specify --- One Reporting -------------------------------------- ----- ----- below) Person (City) (State) (Zip) ---------------------------- (give title below) X Form filed by --- More than One ------------------------------ Reporting Person ----------------------------------------------------------------------------------------------------------------------------------- TABLE I -- NON-DERIVATIVE SECURITIES BENEFICIALLY OWNED ----------------------------------------------------------------------------------------------------------------------------------- 1. Title of Security 2. Amount of Securities 3. Ownership Form: 4. Nature of Indirect (Instr. 4) Beneficially Owned Direct (D) or Beneficial (Instr. 4) Indirect (I) Ownership (Instr. 5) (Instr. 5) ----------------------------------------------------------------------------------------------------------------------------------- By indirect wholly owned Common Stock 17,331,215(1) I subsidiary ----------------------------------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------------------------------- ----------------------------------------------------------------------------------------------------------------------------------- Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly. (Over) *If the form is filed by more than one reporting person, see Instruction 5(b)(v). SEC 1473 (3-99) POTENTIAL PERSONS WHO ARE TO RESPOND TO THE COLLECTIONS OF INFORMATION CONTAINED IN THIS FORM ARE NOT REQUIRED TO RESPOND UNLESS THE FORM DISPLAYS A CURRENTLY VALID OMB CONTROL NUMBER.

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** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a). Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, See Instruction 6 for procedure. Potential persons who are to respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB number. Page 2 of 3 3 JOINT FILER INFORMATION Names and Addresses of Joint Filers: Marathon Oil Company 5555 San Felipe Houston, Texas 77056 Marathon Oil Acquisition 1, Ltd. 5555 San Felipe Houston, Texas 77056 Designated Filer: USX Corporation Issuer Name and Ticker or Trading Symbol: Pennaco Energy, Inc. (PN) Date of Event Requiring Statement (Month/Day/Year): 02/06/01 Signatures: MARATHON OIL COMPANY By /s/ CLARENCE P. CAZALOT, JR. ------------------------------------ Clarence P. Cazalot, Jr. President MARATHON OIL ACQUISITION 1, LTD. By /s/ JOHN T. MILLS ------------------------------------ John T. Mills Vice President Page 3 of 3

PENNACO ENERGY INC 3