According to the U.S. Census Bureau, the county has a total area of, of which is land and is water. It is the second-largest county in Wisconsin by total area. The Apostle Islands are a small group of islands in Lake Superior, off the Bayfield Peninsula with the majority of the islands located in Ashland County — only Sand, York and Raspberry Islands are in Bayfield County.
As of the 2010 United States Census, there were 16,157 people living in the county. 84.6% were White, 11.1% Native American, 0.4% Asian, 0.3% Black or African American, 0.3% of some other race and 3.3% of two or more races. 1.9% were Hispanic or Latino. 25.6% were of German, 7.6% Finnish, 6.8% American, 6.5% Irish and 5.3% Norwegian ancestry. As of the census of 2000, there were 16,866 people, 6,718 households, and 4,279 families living in the county. The population density was 16 people per square mile. There were 8,883 housing units at an average density of 8 per square mile. The racial makeup of the county was 87.10% White, 0.21% Black or African American, 10.35% Native American, 0.31% Asian, 0.05% Pacific Islander, 0.29% from other races, and 1.69% from two or more races. 1.11% of the population were Hispanic or Latino of any race. 27.8% were of German, 8.4% Finnish, 7.4% Polish, 7.4% Norwegian, 7.3% Swedish and 5.4% Irish ancestry. 96.6% spoke English as their first language. The reservation of the Bad River Chippewa Band is partially located in the county. There were 6,718 households out of which 30.30% had children under the age of 18 living with them, 48.60% were married couplesliving together, 10.90% had a female householder with no husband present, and 36.30% were non-families. 30.80% of all households were made up of individuals and 14.40% had someone living alone who was 65 years of age or older. The average household size was 2.39 and the average family size was 3.01. In the county, the population was spread out with 25.40% under the age of 18, 11.20% from 18 to 24, 25.80% from 25 to 44, 21.70% from 45 to 64, and 15.90% who were 65 years of age or older. The median age was 37 years. For every 100 females there were 97.10 males. For every 100 females age 18 and over, there were 91.10 males. In 2017, there were 194 births, giving a general fertility rate of 73.1 births per 1000 women aged 15–44, the eleventh highest rate out of all 72 Wisconsin counties. Additionally, there were no reported induced abortions performed on women of Ashland County residence in 2017.
