Deerfield is a village in Lake and Cook counties in the U.S. state of Illinois. A northern suburb of Chicago, Deerfield is located on the North Shore, about 28 miles north of downtown Chicago. The population was 19,196 at the 2020 census.

Lake County is situated in the northeastern corner of the U.S. state of Illinois, along the shores of Lake Michigan. As of the 2020 census, it has a population of 714,342, making it the third-most populous county in Illinois. Its county seat is Waukegan, the tenth-largest city in Illinois. The county is primarily suburban, with some urban areas and some rural areas. Due to its location, immediately north of Cook County, Lake County is one of the collar counties of the Chicago metropolitan area. Its northern boundary is the Wisconsin state line.