[2] It is named in honor of Lucius Quintus Cincinnatus Lamar, a former Confederate officer and former member of both houses of the United States Congress from Mississippi.

On February 8, 1877, the county was renamed Lamar in honor of Congressman and Senator L.Q.C.

[5] As of the census of 2020, there were 13,972 people, 5,856 households, and 3,895 families residing in the county.

28.8% of all households were made up of individuals, and 13.3% had someone living alone who was 65 years of age or older.

As of the census[15] of 2000, there were 15,904 people, 6,468 households, and 4,715 families living in the county.

25.40% of all households were made up of individuals, and 12.10% had someone living alone who was 65 years of age or older.

In a 2000 referendum to repeal Alabama's constitutional prohibition of interracial marriage, Lamar County voters showed the highest rate of opposition in the state, with 65.69% opposing repeal of the provision.

[16] Lamar County is reliably Republican at the presidential level.

The last Democrat to win the county in a presidential election is Jimmy Carter, who won it by a majority in 1980.