Stillman Valley is a village in Marion Township, Ogle County, Illinois, United States. It lies east of Byron, south of Rockford, and west of Davis Junction. The population was 1,120 at the 2010 census, up from 1,048 at the 2000 census. The village is located on the Iowa, Chicago and Eastern Railroad, on the old Chicago Great Western Railway before it merged and was pulled up. Also, Illinois Route 72 runs through the village, and is near the location for the beginning of the Black Hawk War.