According to the U.S. Census Bureau, the county has a total area of, of which is land and is water.
Climate and weather
In recent years, average temperatures in the county seat of Vandalia 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 July 1980. Average monthly precipitation ranged from in February to in May.
As of the 2010 United States Census, there were 22,140 people, 8,311 households, and 5,648 families living in the county. The population density was. There were 9,302 housing units at an average density of. The racial makeup of the county was 93.7% white, 4.4% black or African American, 0.2% Asian, 0.2% American Indian, 0.4% from other races, and 1.0% from two or more races. Those of Hispanic or Latino origin made up 1.4% of the population. In terms of ancestry, 27.5% were German, 10.5% were English, 9.4% were American, and 9.3% were Irish. Of the 8,311 households, 31.2% had children under the age of 18 living with them, 53.3% were married couplesliving together, 9.7% had a female householder with no husband present, 32.0% were non-families, and 27.2% of all households were made up of individuals. The average household size was 2.45 and the average family size was 2.95. The median age was 39.9 years. The median income for a household in the county was $41,269 and the median income for a family was $51,216. Males had a median income of $38,257 versus $27,188 for females. The per capita income for the county was $21,663. About 10.8% of families and 16.1% of the population were below the poverty line, including 22.6% of those under age 18 and 12.0% of those age 65 or over.
Until the beginning of the twentieth century, Fayette County was rock-ribbed Democratic. It was not won by a Republican until Theodore Roosevelt’s landslide win of 1904. The county voted after that for the winning candidate in every election until 1940, when opposition to Franklin D. Roosevelt’s economic and war policies gave the county to Wendell Willkie. Since then only two Democratic presidential candidates have gained an absolute majority in the county – the more recent of these two, Jimmy Carter in 1976, doing so by a single vote. Like all of the Upland South the county has seen a rapid swing to the Republicans in recent elections due to opposition to the Democratic Party’s liberal views on social issues: Hillary Clinton’s 2016 tally of 19.0 percent of the county’s vote is 15.7 percent worse than any Democrat before 2012.
