Campbell County, WY
Established 1911, Campbell County is part of the Powder River Basin and was valued for many years by American Indians as prime hunting grounds. The first commercial discovery of oil in the county was in 1948, and the first major uranium deposit was found in 1951 at Pumpkin Buttes. Campbell County is the third most-populous county in Wyoming, with a population of 46,140.
Fremont County, WY
One of the richest uranium mines in the state of Wyoming was found in Fremont County. Once a thriving business in the area, uranium mining ceased by the end of the 1980s. Established in 1884, the population has grown to 39,531 in 2018. Over the years, there has been a debate as to whether the county was named for fur-trader Robert Fremont, or famed explorer and U.S. Army officer John C. Fremont, with the latter being the most popular choice.
Laramie County, WY
Named after French-Canadian fur trapper, Jacques La Ramee, Laramie County is one of the original five counties in the state of Wyoming. The state capital, Cheyenne, lies within its borders and is also home to the county seat. The county was officially established in 1867, and with 98,976 residents, Laramie is the most populous county in Wyomying. F.E. Warren Air Force Base is located in Laramie, and is considered by many to be the financial backbone of the county.
Natrona County, WY
Natrona County was established in 1888 and was named for the massive natron deposits in the area. A current population of 79,115 makes Natrona County the second most-populous county in the state of Wyoming. Within its limits sits the Natrona County Airport, which was formerly the home of Casper Army Air Base during World War II.
Sweetwater County, WY
An area rich in natural gas, Sweetwater County is Wyoming’s largest county by area. Spread out over 10,491 mi², it is nearly twice the size of the state of Connecticut. The county was named after the Sweetwater River (a North Platte River tributary) and was officially established in 1867. Boasting a population of 43,051, Sweetwater County is the fourth most-populous county in the state.