Grayslake is a village in Lake County in the U.S. state of Illinois.The village's population at the 2010 census was 20,957.
In 1840, Massachusetts-born William F. Gray settled along the then-unnamed Grays Lake. Other farmers trickled into the area in 1840s. Gray moved toWaukegan in 1845.In 1880, the Wisconsin Central Railroad built a line from Fond du Lac, Wisconsin, to Chicago which passed by the east side of Grays Lake. In 1886, the railroad built a station there, naming it Grayslake. The village incorporated in 1895.