According to Goodspeed's History of Lincoln County, Missouri, Lincoln County was named by Major Christopher Clark, the first permanent white settler in an address to the Territorial Legislature. He said, "I was born, sir, in Link-Horn County, N.C., I lived for many years in Link-Horn County in old Kain-tuck. I wish to die in Link-Horn County, in Missouri; and I move, therefore, that the blank in the bill be filled with the name Link-Horn." The motion was carried unanimously and the clerk, not adopting the frontier parlance of the Major, wrote "Lincoln" in the blank space of the bill. Others say it was named for Major General Benjamin Lincoln, who served in the Continental Army during the American Revolution.
According to the U.S. Census Bureau, the county has a total area of, of which is land and is water. The county's eastern border with Illinois is formed by the Mississippi River.
As of the census of 2000, there were 38,944 people, 13,851 households, and 10,554 families residing in the county. The population density was 62 people per square mile. There were 15,511 housing units at an average density of 25 per square mile. The racial makeup of the county was 96.13% White, 1.74% Black or African American, 0.37% Native American, 0.17% Asian, 0.03% Pacific Islander, 0.43% from other races, and 1.14% from two or more races. Approximately 1.14% of the population were Hispanic or Latino of any race. 37.7% were of German, 17.0% American, 10.9% Irish and 7.4% English ancestry. There were 13,851 households out of which 40.00% had children under the age of 18 living with them, 61.50% were married couples living together, 10.10% had a female householder with no husband present, and 23.80% were non-families. 19.70% of all households were made up of individuals and 7.70% had someone living alone who was 65 years of age or older. The average household size was 2.77 and the average family size was 3.17. In the county, the population was spread out with 30.00% under the age of 18, 8.10% from 18 to 24, 30.20% from 25 to 44, 21.00% from 45 to 64, and 10.80% who were 65 years of age or older. The median age was 34 years. For every 100 females there were 98.40 males. For every 100 females age 18 and over, there were 97.90 males. The median income for a household in the county was $42,592, and the median income for a family was $47,747. Males had a median income of $35,564 versus $23,270 for females. The per capita income for the county was $17,149. About 6.20% of families and 8.30% of the population were below the poverty line, including 9.60% of those under age 18 and 9.00% of those age 65 or over.
The Republican Party mostly controls politics at the local level in Lincoln County. Republicans hold all but five of the elected positions in the county.
District 40 — . Consists of the northernmost section of the county.
District 41 — . Consists of most of the entire county and includes the communities of Cave, Elsberry, Foley, Hawk Point, Silex, Troy, Truxton, and Whiteside.
Former U.S. Senator Hillary Clinton received more votes, a total of 3,490, than any candidate from either party in Lincoln County during the 2008 presidential primary.
