According to the U.S. Census Bureau, the county has a total area of, of which is land and is water. It is the largest county in Illinois by land area and third-largest by total area. McLean County is actually larger than the land area of Rhode Island.
Climate and weather
In recent years, average temperatures in the county seat of Bloomington have ranged from a low of in January to a high of in July, although a record low of was recorded in January 1985 and a record high of was recorded in June 1988. Average monthly precipitation ranged from in February to in May.
As of the 2010 United States Census, there were 169,572 people, 65,104 households, and 40,124 families residing in the county. The population density was. There were 69,656 housing units at an average density of. The racial makeup of the county was 84.3% white, 7.3% black or African American, 4.3% Asian, 0.2% American Indian, 1.5% from other races, and 2.3% from two or more races. Those of Hispanic or Latino origin made up 4.4% of the population. In terms of ancestry, 31.2% were German, 15.4% were Irish, 11.4% were American, and 11.0% were English. Of the 65,104 households, 31.4% had children under the age of 18 living with them, 48.5% were married couplesliving together, 9.6% had a female householder with no husband present, 38.4% were non-families, and 28.1% of all households were made up of individuals. The average household size was 2.44 and the average family size was 3.02. The median age was 32.1 years. The median income for a household in the county was $57,642 and the median income for a family was $77,093. Males had a median income of $52,271 versus $39,685 for females. The per capita income for the county was $28,167. About 6.2% of families and 12.9% of the population were below the poverty line, including 11.4% of those under age 18 and 5.5% of those age 65 or over.
McLean County has a twenty-member board representing ten districts within the county. Districts 1-3 encompass all of the county outside of Bloomington and Normal. Districts 4-6 are within the town limits of Normal, and districts 7-10 are within Bloomington city limits.
Politics
McLean County is historically a Republican-leaning county. The only Democrats to gain an absolute majority of the county's vote since the Civil War have been Franklin D. Roosevelt in 1932 and 1936 and Lyndon Johnson by a mere 420 votes out of over 38,000 total in 1964. Illinois resident Barack Obama in 2008 and Woodrow Wilson in 1912 both carried the county by narrow pluralities. McLean has trended Democratic, sufficiently so that Hillary Clinton in 2016 lost the county by just 1.3 percent despite failing to win the Presidency.
