Lafayette County is a county located in the western portion of the U.S. state of Missouri and is part of the Kansas City metropolitan area. As of the 2010 census, the population was 33,381. Its county seat is Lexington. The county was organized November 16, 1820 from Cooper County and originally named Lillard County for James Lillard of Tennessee, who served in the first state constitutional convention and first state legislature. It was renamed Lafayette County on February 16, 1825, in honor of Revolutionary War hero the Marquis de La Fayette, who was then visiting the United States.
According to the U.S. Census Bureau, the county has a total area of 639 square miles (1,660 km), of which 628 square miles (1,630 km) is land and 11 square miles (28 km) (1.6%) is water.
As of the census of 2000, there were 32,960 people, 12,569 households, and 9,099 families residing in the county. The population density was 52 people per square mile (20/km²). There were 13,707 housing units at an average density of 22 per square mile (8/km²). The racial makeup of the county was 95.52% White, 2.27% Black or African American, 0.29% Native American, 0.25% Asian, 0.03% Pacific Islander, 0.51% from other races, and 1.12% from two or more races. Approximately 1.17% of the population were Hispanic or Latino of any race. 37.3% were of German, 17.5% American, 9.9% English and 9.7% Irish ancestry.
There were 12,569 households out of which 33.90% had children under the age of 18 living with them, 59.30% were married couples living together, 9.40% had a female householder with no husband present, and 27.60% were non-families. 24.00% of all households were made up of individuals and 11.20% had someone living alone who was 65 years of age or older. The average household size was 2.55 and the average family size was 3.01.
In the county, the population was spread out with 26.20% under the age of 18, 7.60% from 18 to 24, 27.50% from 25 to 44, 23.30% from 45 to 64, and 15.40% who were 65 years of age or older. The median age was 38 years. For every 100 females there were 95.90 males. For every 100 females age 18 and over, there were 92.00 males.
The median income for a household in the county was $38,235, and the median income for a family was $45,717. Males had a median income of $31,972 versus $22,684 for females. The per capita income for the county was $18,493. About 6.90% of families and 8.80% of the population were below the poverty line, including 10.90% of those under age 18 and 9.10% of those ages 65 or over.