Shippen-Wistar House, at the corner of 4th Street and Locust, was built about 1750 by William Shippen, M.D., a prominent physician who served in the Continental Congress. Richard Henry Lee, Francis Lightfoot Lee, John Adams, and George Washington were among the guests known to have visited. In 1798 the house was sold to Caspar Wistar, M.D., another of Philadelphia’s famed physicians and one of the early advocates of vaccination.