At the turn of the twentieth century the United States was swiftly becoming a global economic powerhouse thanks to the rapid industrialization of the past thirty years. This growth was fueled by European capital and an influx of immigrants from southern and eastern Europe. For the migrants, the US was a land of opportunity, even if that opportunity was shitty factory jobs in heavily polluted urban areas. Either way, it was seen as much better than the poverty and lack of any chance of bettering oneself in their home countries. Millions of migrants poured in. The industrial barons made their million and billions of dollars. Everyone seemed quite happy with the arrangement. Well, maybe not everyone. One group that was rather unhappy with everything was the labor unions, who saw the constant influx of uneducated immigrants as one of the obstacles of widespread unionization. Another group were political purists, which is a nice way of saying super racist people, who viewed anyone not having what they referred to as northern European blood as being inferior.
While both of these groups pushed for immigration controls for decades, wide public support wasn't swayed until the outbreak of an economic recession following World War I put hundreds of thousands of people out of work, many of them veterans of the war. Not really wanting a huge number of pissed off people with military training just sitting around, the U.S. government responded by passing the Emergency Quota Act in 1921, which severely limited the number of people who could immigrate to the US, especially those seen as undesirable (aka not northern European). This was followed by the Immigration Act of 1924 which further curtailed immigration and outright banned some groups. Immigration to the US fell by half in 1921 and fell by half again in 1924, effectively ending a period of open immigration in place since the country's inception.
While the labor unions and random racists were very happy with this turn of events, the industrial barons were less than pleased given that their cheap source of labor had suddenly disappeared, forcing them to actually deal with the labor unions and their demands for higher wages and safer working conditions. Not really wanting to deal with the higher costs of not treating people like shit, the industrial barons began looking around for a new supply of cheap labor. That's when African-Americans get involved in this story. At the beginning of the 20th century, 90 percent of the black people in the U.S. were in the south. Most were uneducated and lived in rural areas, working as field hands for the shittiest of wages. While greater opportunities were available elsewhere, especially in the growing factory cities of the Midwest, the rampant racism of the time barred them to blacks. However, cracks first started appearing in these beliefs as World War I removed millions of young men from the workforce, forcing factory owners to reassess their views. The passage of immigration controls turned the crack into a breach.
By 1930 over 1.6 million African-Americans had immigrated north to find better paying jobs in factories. Not only were there better wages, but also less codified segregation and less lynching. The factory owners for their part provided free transportation and low cost housing to attract in more workers. It of course goes without saying that this didn't come without some hiccups. Though there were no laws requiring segregation in many areas, the locals were less than happy with the influx of African-Americans into their communities. It was a bad combination of economic worries and stupidly racist ideas. They did everything they could to make the newcomers feel unwelcome. The labor unions were amongst the worst groups when it came to the great migration of blacks within the U.S. The shift of people north also affected the south. Farms, used to paying abysmally low wages shifted more towards mechanization. Southern factories were forced to raise their own wages to retain workers. A significant number of African-Americans were propelled upward out of poverty, creating greater opportunities for better education which helped create the luminaries who would lead the Civil Rights movement of the 1960's.
Though the Great Migration slowed during the Great Depression, the continued policies limiting immigration and the outbreak of World War II helped ensure its renewal once the U.S. shook off its economic woes. Between 1940 and 1970 a further five million African-Americans left the South looking for a taste of the opportunities enjoyed by their white counterparts. By 1970, half of the black population in the U.S. lived outside the southern states that had once enslaved them. With blacks living across the country, their existence and their treatment became more than just a southern problem. The large number who lifted themselves up once given the opportunity forced many to reevaluate their ridiculous views on race. Though we still have a ways to go today, it was the spark for the start of real change, and it was all thanks to capitalist greed and anti-immigrant rhetoric. The world is a complicated place.