According to the U.S. Census Bureau, the county has a total area of, of which is land and is water. It is the fifth-largest county in Wisconsin by land area.
Sawyer County Highway B is the busiest rural roadway on average in all of Sawyer County with a high count of 5900 vehicles daily, according to the Wisconsin Department of Transportation's average daily traffic maps for 2008. https://web.archive.org/web/20100602030241/http://www.dot.wisconsin.gov/travel/counts/docs/sawyer/sawyer2008.pdf
As of the census of 2000, there were 16,196 people, 6,640 households, and 4,581 families residing in the county. The population density was 13 people per square mile. There were 13,722 housing units at an average density of 11 per square mile. The racial makeup of the county was 81.72% White, 0.31% Black or African American, 16.07% Native American, 0.30% Asian, 0.02% Pacific Islander, 0.35% from other races, and 1.23% from two or more races. 0.90% of the population were Hispanic or Latino of any race. 29.6% were of German, 7.8% Irish, 6.7% Norwegian, 5.9% Polish, 5.2% Swedish and 5.2% English ancestry. 95.4% spoke English, 2.0% Ojibwa and 1.1% Spanish as their first language. There were 6,640 households out of which 27.50% had children under the age of 18 living with them, 54.20% were married couplesliving together, 10.00% had a female householder with no husband present, and 31.00% were non-families. 26.20% of all households were made up of individuals and 11.70% 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 2.86. In the county, the population was spread out with 24.10% under the age of 18, 6.00% from 18 to 24, 24.60% from 25 to 44, 27.40% from 45 to 64, and 17.90% who were 65 years of age or older. The median age was 42 years. For every 100 females there were 101.80 males. For every 100 females age 18 and over, there were 101.00 males. In 2017, there were 167 births, giving a general fertility rate of 74.5 births per 1000 women aged 15–44, the 8th highest rate out of all 72 Wisconsin counties. Additionally, there were fewer than five reported induced abortions performed on women of Sawyer County residence in 2017.
Sawyer County is a bellwether county in presidential elections, having voted for the overall national winner in every election from 1964 onward and only not voting for the national winner in 1960 from 1952 onward.