February 15 is a big day in the history of Wyoming Places. Three counties—Park in 1909, and Sublette and Teton in 1921—were created by the Wyoming Legislature. Numerous post offices were established including Twin Creeks in 1883, Lusk in 1884, Fossil in 1886, Hematite in 1889, Campbell in 1890, and Arapahoe Agency and Little Medicine in 1893.
1893 Arapahoe Post Office was established as Arapahoe Agency Post Office on February 15, 1893. Its name changed to Arapahoe on May 12, 1906. Arapahoe was named for the Arapaho people who lived there.