Pennsylvania--Politics and Government Economic Recessions--18th century 1 Iron industry and trade--Pennsylvania 1 Pennsylvania--History--Colonial period, ca. 1600-1775--Sources 1 Slavery--Legal aspects--18th century 1 Steamboat--18th century 1 United States--Foreign Relations--18th century 1 more ... United States--Politics--18th century 1 United States--Politics--19th century 1 less ...