Natrona is one of the 23 counties in the state of Wyoming. It was created in 1888 from part of Carbon county. As of the 2010 census, the population was 75,450. The county seat is Casper. The county has 5,376 square miles in area. The county is bordered by Johnson County to the north, Converse County to the east, Carbon County to the south, Fremont County to the west, and Washakie County to the northwest.