Plainfield is a village in Will and Kendall counties, Illinois, United States. The population was 44,762 at the 2020 census.

Will County is a county in the northeastern part of the state of Illinois. According to the 2020 census, it had a population of 696,355, an increase of 2.8% from 677,560 in 2010, making it Illinois's fourth-most populous county. The county seat is Joliet. Will County is one of the five collar counties of the Chicago–Naperville–Elgin, IL–IN–WI Metropolitan Statistical Area. The portion of Will County around Joliet uses area codes 815 and 779, while 630 and 331 are for far northern Will County and 708 is for central and eastern Will County.