 Complete the following phrase:  In 1861, William Selden, Treasurer of the United States from 1839 to 1850, owned of land north of Pierce Mill Road. In 1862, during the American Civil War, Selden, a Confederate sympathizer, was forced to sell his land at a low price and move back to his native Virginia. The purchaser was New England native Samuel P. Brown. Brown built a house and allowed the Mount Pleasant General Hospital to be constructed on his land. In June 1863, Walt Whitman saw a train of about thirty huge four-horse wagons, used as ambulances, filled with wounded, passing up Fourteenth street traveling from the 