Lecompton is a city in Douglas County, Kansas, United States. As of the 2020 census, the population of the city was 588. Lecompton, located on the Kansas River, was the de jure territorial capital of Kansas from 1855 to 1861, and the Douglas County seat from 1855 to 1858. Anti-slavery Lawrence became the de facto capital during the latter part of this period, when the county seat was moved there.