with the manpower mobilization of world war i and immigration from europe cut off, the industrial cities of the northeast and midwest experienced severe labor shortages. northern manufacturers recruited throughout the south and an exodus of workers ensued. by 1919, an estimated 500,000 african americans had emigrated from the southern united states to the industrial cities in the northeast and midwest in the first wave of the great migration, which continued until 1940. african-american workers filled new positions in expanding industries, such as the railroads, as well as many jobs formerly held by whites. in some cities, they were hired as strikebreakers, especially during the strikes of 1917. this increased resentment against blacks among many working-class whites, immigrants or first-generation americans. in the summer of 1917, violent racial riots against blacks, due to labor tensions, broke out in east st. louis, illinois and houston, texas. following the war, rapid demobilization of the military without a plan for absorbing veterans into the job market, and the removal of price controls, led to unemployment and inflation that increased competition for jobs. jobs were very difficult for african americans to get in the south due to the racism and segregation still present in the south.