where is swansea,_illinois and where is belleville, il
Wikimedia Commons: Swansea, Illinois Swansea is a village in St. Clair County, Illinois. The population was 13,430 at the 2010 census, an increase from 10,579 in 2000.
It is the county seat of St. Clair County, and the seat of the Roman Catholic Diocese of Belleville, Belleville is the most populated city in the Metro-East region of the St. Louis Metropolitan Area and in Southern Illinois.