is the only city in and the county seat of Natrona County, Wyoming, United States. With a population of 49,644, Casper is the second largest city in Wyoming, according to the 2000 census. Casper is nicknamed "The Oil City" and has a long history of oil boomtown and cowboy culture, dating back to development of the nearby Teapot Dome. During the early 1980s, Casper was the largest city in Wyoming; according to U.S. Census figures for 1980, Casper had a population of 51,016 compared with Cheyenne's 47,283.
Casper is located in east-central Wyoming at the foot of Casper Mountain, the north end of the Laramie Mountain Range, along the North Platte River. Interstate 25 approaches Casper from the North and East and is the main avenue of transportation to and from the city. The towns immediately adjacent to Casper are Mills, Evansville, Bar Nunn, and Mountain View. Unincorporated areas include Allendale, Dempsey Acres, Red Buttes, Indian Springs, and several others.
The city was established east of the former site of Fort Caspar, which was built during the mid-19th century mass migration of land seekers along the Oregon, California and Mormon trails.
. The area was the location of several ferries that offered passage across the North Platte River in the early 1840s. In 1859, Louis Guinard built a bridge and trading post near the original ferry locations.
The government soon posted a military garrison nearby to protect telegraph and mail service. It was under the command of Lieutenant Colonel William O. Collins. American Indian attacks increased after the Sand Creek Massacre in Colorado in 1864, bringing more troops to the post, which was by now called Platte Bridge Station. In July 1865, Lieutenant Caspar Collins (the son of Colonel Collins) was killed near the post by a group of Indian warriors. Three months later the garrison was renamed Fort Caspar after Lieutenant Collins. In 1867, the troops were ordered to abandon Fort Caspar in favor of Fort Fetterman downstream on the North Platte along the Bozeman Trail.
The town of Casper itself was founded well after the fort had been closed. The city was founded by developers as an anticipated stopping point during railroad expansion; it was an early commercial rival to Bessemer and Douglas, Wyoming. The lack of a railhead doomed Bessemer in favor of Casper. Douglas, also a railhead, survives to the present day. The presence of a railhead made Casper the starting off point for the "invaders" in the Johnson County War. The special chartered train carrying the men up from Texas stopped at Casper.