Fergus County, located in Montana, has a population of 11,751 with a population density of 2.7 people per square mile. The demographic breakdown shows a predominantly white population of 11,193, with smaller minority populations including Black (25), American Indian or Alaska Native (143), Asian (27), Hispanic (171), and individuals of multiple races (176). The county has slightly more males (5,821) than females (5,765), and the median age is 47.6, with a higher median age for females (48.5) compared to males (46.7). The average household size is 2.18, and there are 5,099 households in the county, with 3,725 owner-occupied and 1,374 renter-occupied households. In terms of family structure, there are 861 married households with children and 1838 married households with no children, while there are 107 male-headed households with children and 222 female-headed households with children.

In comparison to other counties in Montana, Fergus County has a lower population density and total population size. The county has a higher proportion of white residents compared to some other counties in the state, with only small numbers of Black, American Indian, Asian, and Hispanic individuals. The county also has a higher median age compared to the state average, suggesting an older population. In terms of household composition, Fergus County has a relatively low average household size and a higher percentage of owner-occupied households compared to renter-occupied households. The county also has a significant number of farms, with 845 farms in 2017 covering a total of 623,933 acres of cropland.