About the town » Cortland, DeKalb County, Illinois, United States

Cortland is an incorporated town in DeKalb County, Illinois, United States. The population was 4,270 at the 2010 census, up from 2,066 at the 2000 census. Because of its status as an incorporated town, Cortland has adopted the slogan, "The Third Largest Town in Illinois. " Only the towns of Cicero and Normal are larger, in terms of population.