King of Prussia is a census-designated place in Upper Merion Township, Montgomery County, Pennsylvania, United States. As of the 2010 census, its population was 19,936.
The eponymous King of Prussia Inn was originally constructed as a cottage in 1719 by the Welsh Quakers William and Janet Rees, founders of nearby Reeseville. The cottage was converted to an inn in 1769 and did a steady business in colonial times as it was approximately a day's travel by horse from Philadelphia. Settlers headed west to Ohio would sleep at the inn on their first night on the road. In 1774 the Rees family hired James Berry to manage the inn, which henceforth became known as "Berry's Tavern". General George Washington first visited the tavern on Thanksgiving Day in 1777 while the Continental Army was encamped at Whitemarsh; a few weeks later Washington and the army bivouacked at nearby Valley Forge.Parker's spy map, created by a Tory sympathizer of the Kingdom of Great Britain, listed the inn as "Berry's" in 1777, but a local petition in 1786 identified it as the "King of Prussia". It was possibly renamed in honor of Benjamin Franklin's pro-American satirical essay "An Edict by the King of Prussia". At some point a wooden signboard of the inn depicted King Frederick II (Frederick the Great) of Prussia. The inn is listed on the National Register of Historic Places.