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Cheyenne Headquarters Office:
United States Attorney’s Office
J.C. O’Mahoney Federal Courthouse
2120 Capitol Avenue, Suite 4000
Cheyenne, WY 82001

Post Office Box 668, Cheyenne, WY 82003-0668

Cheyenne Main Number: (307) 772-2124
Cheyenne Toll-Free Number: (800) 836-5801

Casper Branch Office:
United States Attorney’s Office
Dick Cheney Federal Building
100 East B Street, Suite 2211
Casper, WY 82601

Post Office Box 22211, Casper, WY 82602-5010

Casper Main Number: (307) 261-5434
Casper Toll-Free Number: (800) 809-7066

Lander Branch Office:
United States Attorney’s Office
331 Main Street, Suite A
Lander, WY 82520

Post Office Box 449, Lander, WY 82520-0449

Lander Main Number: (307) 332-8195
Lander Toll-Free Number: (888) 266-1309

Yellowstone National Park Branch Office
United States Attorney’s Office
Yellowstone Justice Center
Building #MA-1015, Room 213
Mammoth Hot Springs, WY 82190

Post Office Box 22211, Casper, WY 82602-5010

Calls are currently being directed through the Casper Office.

Office Hours

Office Hours:

The U.S. Attorney’s Office is open for business from 8:00 a.m. to 5:00 p.m., Monday through Friday, except on federal holidays.

Federal Holidays:

Follow this link for a listing of federal holidays that are observed by the federal government and to determine which days the holidays fall upon.


Public Information Officer:

Contact the Public Affairs Officer in Cheyenne or send e-mail to: Public Information Officer


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Updated September 8, 2022