Jeffrey City is a former uranium mining boomtown located in Fremont County, in the central part of the U.S. state of Wyoming. The town is known in Wyoming and the American West as symbol of a boomtown that went "bust" very quickly, as the mine was shut down in 1982 and over 95% of the inhabitants left the town within three years. The population was 58 at the 2010 census, far lower than its onetime population of several thousand people. For statistical purposes, the United States Census Bureau has defined Jeffrey City as a census-designated place (CDP).

Fremont County is a county in the U.S. state of Wyoming. As of the 2020 United States census, the population was 39,234, making it the fifth-most populous county in Wyoming. Its county seat is Lander. The county was founded in 1884 and is named for John C. Frémont, a general, explorer, and politician. It is roughly the size of the state of Vermont.