East St. Louis in 1917 had a strong industrial economy boosted by America's economic participation in demands related to World War I; although war was declared in April, the nation did not meaningfully enter the war until that fall. Industry was dominated by European immigrant workers, who had been coming to industrial cities since the late 19th century. Here and across the country, they repeatedly tried to organize in efforts to gain better wages and working conditions. In the summer of 1916, 2,500 white workers struck the nearby meat packing plants of National City. Companies recruited black workers, sometimes importing them from the South. While the white workers won a wage increase, the companies retained some black workers, firing white ones. Such economic competition raised tensions between the groups in a period when the number of blacks in East St. Louis had increased dramatically due to the first Great Migration, when African Americans left poor rural areas of the South to escape Jim Crow oppression and seek jobs in the industrial cities of the North and the Midwest. From 1910 to 1917, the black population nearly doubled in East St. Louis.