[2] Floyd County was established in 1854 and was named for Sergeant Charles Floyd[3] of the Lewis and Clark Expedition, who died in 1804 near what is now Sioux City, Iowa, and who was the only member to die on the Expedition.

[13] As of the census[14] of 2000, there were 16,900 people, 6,828 households, and 4,711 families residing in the county.

The racial makeup of the county was 98.11% White, 0.23% Black or African American, 0.09% Native American, 0.43% Asian, 0.09% Pacific Islander, 0.44% from other races, and 0.60% from two or more races.

There were 6,828 households, out of which 30.50% had children under the age of 18 living with them, 57.70% were married couples living together, 7.70% had a female householder with no husband present, and 31.00% were non-families.

28.00% of all households were made up of individuals, and 14.60% had someone living alone who was 65 years of age or older.

Floyd County is divided into twelve townships: The population ranking of the following table is based on the 2020 census of Floyd County.

In only four elections from 1896 to 1984 did a Republican presidential candidate fail to win the county.