<Tr> <Th> Area code (s) </Th> <Td> 610 and 484 </Td> </Tr> <Tr> <Th> GNIS feature ID </Th> <Td> 1178473 </Td> </Tr> <P> King of Prussia (also referred to as KOP) 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 King Frederick the Great of Prussia . Like the rest of Montgomery County, King of Prussia continues to experience rapid development . The largest shopping mall in the United States, the King of Prussia Mall, is located here . Also located here is the headquarters of the Nuclear Regulatory Commission Region I. King of Prussia is considered to be an edge city of Philadelphia, consisting of large amounts of retail and office space situated at the convergence of four highways . </P> <P> The eponymous King of Prussia Inn was originally constructed as a cottage in 1719 by the Welsh Quakers William and Janet Rees, founders of Reesville . 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 . </P>

Where did king of prussia get its name