Morrison is a city in Whiteside County, Illinois, United States. The population was 4,188 at the 2010 census, down from 4,447 in 2000. It is the county seat of Whiteside County. It is located on the Historic Lincoln Highway, the nation's first transcontinental highway and in Morrison was the site of two concrete "seedling miles", which served as prototypes of what an improved highway could do for the nation.