The Capitol developed into its current majestic form through enlargements and a new dome that were designed by Thomas U. Walter of Philadelphia. When he came to Washington in 1851, Walter was already one of the nation’s leading architects. He had designed Girard College in Philadelphia, private mansions and villas, churches, commercial buildings, and engineering projects located up and down the east coast and as far away as Venezuela. It was, however, his work for the federal government—especially the Capitol’s great iron dome—that placed him at the pinnacle of the architectural profession and secured his enduring place in American history.