Penn died in 1718, and was succeeded as proprietor of the colony by his sons. While Penn had won the respect of the Lenape for his honest dealing, Penn's sons and agents were less sensitive to Native American concerns. The 1737 Walking Purchase expanded the colony, but caused a decline in relations with the Lenape. Pennsylvania continued to expand and settle in the areas to the West until the Royal Proclamation of 1763, which forbade all settlers from settling on the western side of the Appalachian Mountains. Meanwhile, Philadelphia became an important port and trading center. The University of Pennsylvania was founded during this period, and Benjamin Franklin established various other organizations such as the American Philosophical Society, the Union Fire Company, and the Pennsylvania Abolition Society. By the start of the American Revolution, Philadelphia was the largest city in British North America.