Canals and railroads--19th century 1 Centennial Exhibition (1876 : Philadelphia, Pa.) 1 Delaware & Schuylkill Canal 1 Engineering--Pennsylvania--Philadelphia 1 Family life--Pennsylvania--18th century 1 Family life--Pennsylvania--19th century 1 Family life--Pennsylvania--20th century 1 more ... Korean War, 1950-1953 1 Pennsylvania Railroad--19th century 1 Quakers--Pennsylvania--18th century 1 Railroads--Pennsylvania--19th century 1 Separation and divorce--19th century 1 Smallpox--Pennsylvania--Philadelphia 1 Spouses--Correspondence--18th century 1 Spouses--Correspondence--19th century 1 Spouses--Correspondence-–20th century 1 United States--History--Revolution, 1775-1783 1 World War, 1939-1945 1 less ...