1 EXHIBIT 3.1 PAGE 1 State of Delaware Office of the Secretary of State --------------------------------- I, EDWARD J. FREEL, SECRETARY OF STATE OF THE STATE OF DELAWARE, DO HEREBY CERTIFY THE ATTACHED ARE TRUE AND CORRECT COPIES OF ALL DOCUMENTS ON FILE OF "RELIANT ENERGY MID-ATLANTIC POWER HOLDINGS, LLC" AS RECEIVED AND FILED IN THIS OFFICE. THE FOLLOWING DOCUMENTS HAVE BEEN CERTIFIED: CERTIFICATE OF FORMATION, FILED THE TWENTY-EIGHTH DAY OF DECEMBER, A.D. 1998, AT 4:30 O'CLOCK P.M. CERTIFICATE OF AMENDMENT, FILED THE TWENTY-FIRST DAY OF MARCH, A.D. 1999, AT 9 O'CLOCK A.M. CERTIFICATE OF AMENDMENT, CHANGING ITS NAME FROM "SITHE PENNSYLVANIA HOLDINGS LLC" TO "RELIANT ENERGY MID-ATLANTIC POWER HOLDINGS, LLC", FILED THE TWELFTH DAY OF MAY, A.D. 2000, AT 3 O'CLOCK P.M. AND I DO HEREBY FURTHER CERTIFY THAT THE AFORESAID CERTIFICATES ARE THE ONLY CERTIFICATES ON RECORD OF THE AFORESAID LIMITED LIABILITY COMPANY. [SEAL] /s/ EDWARD J. FREEL ------------------------------------ Edward J. Freel, Secretary of State 2985509 8100H AUTHENTICATION: 0629340 001421441 DATE: 08-21-00 2 STATE OF DELAWARE SECRETARY OF STATE DIVISION OF CORPORATIONS FILED 04:30 PM 12/28/1998 981505018 - 2985509 CERTIFICATE OF FORMATION OF SITHE PENNSYLVANIA HOLDINGS LLC The undersigned, an authorized natural person, for the purposes of forming a limited liability company, under the provisions and subject to the requirements of the State of Delaware (particularly Chapter 18, Title 6 of the Delaware Code and the acts amendatory thereof and supplemental thereto, and known, identified, and referred to as the "Delaware Limited Liability Company Act"), hereby certifies that: FIRST: The name of the limited liability company (hereinafter called the "limited liability company") is: SITHE PENNSYLVANIA HOLDINGS LLC SECOND: The address of the registered office and the name and the address of the registered agent of the limited liability company required to be maintained by Section 18-104 of the Delaware Limited Liability Company Act are: The Corporation Trust Company Corporation Trust Center 1209 Orange Street Wilmington, New Castle County, Delaware 19801 Executed on December 28, 1998. /s/ GEORGE LOFASO ----------------------- George Lofaso Authorized Person 3 CERTIFICATE OF AMENDMENT OF CERTIFICATE OF FORMATION OF SITHE PENNSYLVANIA HOLDINGS LLC 1. The name of the limited liability company is Sithe Pennsylvania Holdings LLC 2. The Certificate of Formation of the limited liability company is hereby amended as follows: The present SECOND paragraph shall be deleted in its entirety and replaced with the following new SECOND paragraph: SECOND: The address of the registered office and the name and address of the registered agent of the limited liability company required to be maintained by Section 18-104 of the Delaware Limited Liability Company Act are: United Corporate Services, Inc. 15 East North Street Dover, Kent County, Delaware 19901 IN WITNESS WHEREOF, the undersigned has executed this Certificate of Amendment of Sithe Pennsylvania Holdings LLC this 31st day of March, 1999. Sithe Mid-Atlantic, Inc., as sole member By: /s/ DAVID L. TOHIR -------------------------------- Name: David L. Tohir Title: President STATE OF DELAWARE SECRETARY OF STATE DIVISION OF CORPORATIONS FILED 09:00 AM 03/31/1999 991127301 - 2985509 4 STATE OF DELAWARE SECRETARY OF STATE DIVISION OF CORPORATIONS FILED 03:00 PM 05/12/2000 001245618 - 2985509 CERTIFICATE OF AMENDMENT OF CERTIFICATE OF FORMATION OF SITHE PENNSYLVANIA HOLDINGS LLC 1. The name of the limited liability company is Sithe Pennsylvania Holdings LLC. 2. The Certificate of Formation of the limited liability company is hereby amended as follows: The present FIRST paragraph shall be deleted in its entirety and replaced with the following new FIRST paragraph: "FIRST: The name of the limited liability company (hereinafter called the "limited liability company") is: Reliant Energy Mid-Atlantic Power Holdings, LLC" The present SECOND paragraph shall be deleted in its entirety and replaced with the following new SECOND paragraph: "SECOND: The address of the registered office and the name and the address of the registered agent of the limited liability company required to be maintained by Section 18-104 of the Delaware Limited Liability Company Act are: The Corporation Trust Company 1209 Orange Street New Castle County Wilmington, Delaware 19801" 5 IN WITNESS WHEREOF, the undersigned has executed this Certificate of Amendment of Sithe Pennsylvania Holdings LLC this 12th day of May, 2000. Reliant Energy Northeast Generation, Inc., as sole member By: /s/ J. DOUGLAS DIVINE -------------------------------------- J. Douglas Divine President