Sheridan is one of the 23 counties in the state of Wyoming. It was created in 1888 from part of Johnson county. As of the 2010 census, the population was 29,116. The county seat is Sheridan. The county has 2,527 square miles in area. The county is bordered by Big Horn County, Montana to the north, Powder River County, Montana to the northeast, Campbell County to the east, Johnson County to the south, and Big Horn County to the west.