Lanark is a city in Carroll County, Illinois, United States. The population was 1,457 at the 2010 census, down from 1,584 at the 2000 census.
Under the auspices of the Chicago, Milwaukee, St. Paul and Pacific Railroad, Daniel W. Dame purchased 500 acres, laid out the city of Lanark, and was elected its first mayor in 1861. In 1886, 40 residents each donated one dollar to form a public library, and a primary and secondary school was completed in August 1867. On November 25, 1893, the original school was destroyed by fire.
Early in the Twentieth Century, Lanark was home to the Cotta steam car company.