The Old Lock Pump House, whose first element was built in 1837, preserves a feature of the old canal, which relied on locks and pumps to move vessels over the low divide of the Delmarva Peninsula between Chesapeake Bay and Delaware Bay. Because there are no large rivers on the peninsula, water had to be pumped uphill to fill the upper canal and locks. When the canal was cut deeper in the twentieth century, such measures were no longer required, and the pump house is one of the last relics of the old canal.The landmark district is part of a row of buildings at the Back Creek Mooring Basin on the south side of the basin in Chesapeake City, Maryland. The buildings were built between 1837 and 1854 of fieldstone, brick and clapboard.