King of Prussia is an unincorporated community in Upper Merion Township, Montgomery County, Pennsylvania, United States. As of the 2000 census, its population was 18,511. The community took its name in the 18th century from a local tavern named 'The King of Prussia Inn', which was named for Frederick II, King of Prussia. King of Prussia apartments for rent comparison page shows most up to date rent information on King of Prussia apartments and houses. Rent information is obtained from multiple rental sources but we cannot guarantee their accuracy.