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 community took its name in the 18th century from a local tavern named the King of Prussia Inn, which was named after Frederick II, King of Prussia. Like the rest of Montgomery County, King of Prussia continues to experience rapid development. The largest shopping mall in the United States in terms of space and size, the King of Prussia Mall, is located here. Also located here is the headquarters of the Nuclear Regulatory Commission Region I.
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.
The inn was forced to move with the expansion of U.S. Route 202. U.S. 202 is a major north-south highway that passes through the town from southwest to northeast. Its construction as a modern expressway would have caused the destruction of the King of Prussia Inn; however, historic preservationists managed to prevail upon the state of Pennsylvania to avoid this important structure by building north and southbound lanes on either side of it. For more than a quarter century the inn was marooned on a median island, with motor traffic whizzing past on both sides. It was sealed up for years, surrounded by a high fence. The inn was successfully relocated in 2000 and opened to the public in October 2002.
The extensive suburban development that has taken place since the 1960s in King of Prussia has led urban planning scholars like Joel Garreau to label the area as an epitome of the edge city phenomenon, a situation where the most vibrant economic growth and prosperity in a metropolitan area (in this case, Philadelphia) no longer occurs in the urban center, but rather at its periphery. Before 1960, the Greater King of Prussia area was known for little more than being the place of Washington's winter respite in 1777-8 (see Valley Forge National Historical Park).