APA (7th ed.) Citation

United States. National Park Service. (2018). Pony Express: Pony Express National Historic Trail (Last updated 2018.). National Park Service, U.S. Department of the Interior.

Chicago Style (17th ed.) Citation

United States. National Park Service. Pony Express: Pony Express National Historic Trail. Last updated 2018. [Washington, D.C.]: National Park Service, U.S. Department of the Interior, 2018.

MLA (9th ed.) Citation

United States. National Park Service. Pony Express: Pony Express National Historic Trail. Last updated 2018. National Park Service, U.S. Department of the Interior, 2018.