From April 1917 to November 1918 the mobilization of the American economy was extraordinary. War created a number of production demands: guns and ammunition, means of transportation, places to train, food and clothing, and new ships for the Navy.
Increases in the labor force and output of raw materials (steel, copper, rubber, etc.) allowed the economy to meet those demands. The government also increased taxes and sold Liberty Bonds, which helped raise money for government-issued production contracts.
Many of those contracts went to steel companies, which produced iron and steel for munitions, tanks, ships, and more. Coatesville’s companies, Lukens Steel Company and Midvale Steel & Ordnance Company, greatly increased their production and became major suppliers for the Allies in World War I.