High Quality Content by WIKIPEDIA articles! Chesterfield County is a county located in the Commonwealth of Virginia, a state of the United States. In 2010, its population was estimated to be 316,236. Chesterfield County is now the fourth-largest municipality in Virginia (behind Fairfax County, Virginia Beach, and Prince William County, respectively). Its county seat is Chesterfield (Courthouse). It is located in the Richmond-Petersburg region and is a portion of the Richmond Metropolitan Statistical Area (MSA). Much of the northern portion of Chesterfield County accounts for what is referred to as Metropolitan Richmond`s "South Side".