Moving river cargo along the Allegheny was difficult when low bridges prevented large boats from passing through. The 30th Street Bridge was the last obstruction on the Allegheny that interfered with river commerce. When replaced in 1928, the new 31st Street Bridge allowed for the smooth shipment of coal, steel, and many other products to and from Pittsburgh.
Between 1924 and 1928, the Allegheny County Department of Public Works oversaw the construction of 41 new bridges-one of the most aggressive public improvement campaigns to date. Reacting to the Secretary of War's 1917 declaration that all "unreasonable obstructions to the navigation of the Allegheny River" be removed, the county approved the issuance of bonds in the amount of $29 million for new bridges, roads, and buildings to aid the movement of goods and war materials along the rivers.
Because of the new bridges, Pittsburgh became an indispensible supplier during World War II, leading Governor James to call the Keystone State the "Arsenal of America." Pittsburgh's factories began producing weapons, vehicles, aircraft, and parts. The easy shipment of these goods on the rivers helped to ensure an Allied victory in the war.