city, seat (1890) of Natrona county, east-central Wyoming, U.S., on the North Platte River. It originated around Fort Caspar at the site of a pioneer crossing on the Oregon Trail and the Pony Express route. The fort, now restored, was named for Lieutenant Caspar Collins, who was slain by Indians in 1865 while trying to rescue a stranded wagon train. The California, Overland, and Oregon trails met near the site of Casper's establishment. Founded in 1888 as a tent town before the arrival of the Chicago and North Western Railway, the town was named Casper (a misspelling of Collins's name) by clerical error. In the 1890s the Salt Creek Oil Field, just north, established the town's oil business. The oil fields include Teapot Dome, centre of the scandal (Teapot Dome Scandal) that rocked the administration of President Warren G. Harding (Harding, Warren G.) in 1922.

At the turn of the 21st century, Casper's economy was based on the production of oil and natural gas and the manufacture of oil-field equipment, augmented by mining (uranium, coal, bentonite) and cattle and sheep raising. Ranching continues to be important, but the contemporary city mainly depends on a service economy. Casper is the trading centre for a large hinterland and is the seat of Casper College (1945; two-year). Casper Mountain Park and Medicine Bow National Forest are to the southeast. The Central Wyoming Fair and Rodeo is held annually in August. Memorabilia of frontier days are displayed at the Fort Caspar Museum. Inc. town, 1889; city, 1917. Pop. (1990) city, 46,742; Casper MSA, 61,223; (2000) city, 49,644; Casper MSA 66,533.