Answer: I assume you’re asking about the Great Migration of African Americans in the first part of the 20th century?
The first, singular, and overriding cause was the lack of real economic opportunity in the southern United States for blacks. Briefly, during the American Reconstruction period (roughly 1865-1875 or so), newly emancipated blacks (and many free blacks who resettled) found that their economic opportunities had greatly improved. By “greatly improved” I mean that they could now, freely and without (most) prejudice, engage in commerce in an open and mostly (fair) market.
This caused many, many white Southerners discomfort. As I’ve pointed out elsewhere, the Civil War was primarily an economic conflict, with two competing economic visions clashing. With the destruction of a slave-based agrarian economy, white Southerners found themselves in direct economic competition with their former slaves. This caused enormous resentment, even more than the (strong) resentment most whites felt about black enfranchisement. By the Grant administration, the policy of enforced reconstruction was abandoned. Many of the economic gains African Americans enjoyed were put asunder.
By 1900, blacks were reduced to tenant farmers (at best) and sharecroppers (at worst). Although there were some success stories, most were kept in a state of enforced poverty by a racist system. A series of Supreme Court cases only reinforced this position, culminating with Plessy v. Ferguson in 1896, which established the odious model of “separate but equal” in the American socio-economic landscape.
However, coinciding with the rapid constriction of African-American economic and social rights in the South was the equally rapid industrialization in the American upper-Midwest. The Civil War made cities such as Chicago, Detroit and Cleveland boomtowns. The pace of industrialization only increased, so that by 1890, these cities and others were some of the leading manufacturing ares in the country. Manufacturers needed workers, and because of the (relatively) benign racial attitudes of the mid-west, they were happy to hire black workers. At first a trickle, then a flood, of African Americans migrated to the mid-west (and, to a certain extent, the northeast), seeking improved financial situations for themselves and their families. By the first half of the 20th century, a vast number of blacks had relocated to places such as Chicago, creating a new, emergent black middle-class, and transforming the region and it’s fortunes. It really was a win-win for blacks and the bustling mid-western manufacturing hubs. Indeed, the greatest period of migration was from 1910-1940 (see: Great Migration (African American)
A quick word of caution, however. I’m not trying to paint too-rosy of a picture for blacks who relocated to the mid-west. While racial attitudes were less intolerant than in the South, there was still a great deal of racism to be found, and there were lynchings in the midwest as well (see: Lynching in the United States)
It was, however, a lose-lose for the South, both black and white. The blacks that remained were increasingly marginalized, while the South as a whole lagged economically behind the rest of the country. Indeed, the South had never been much of an industrialized region before the Civil War. The war destroyed much of its industrial capacity. That combined with the fact that the primary labor practice of its agricultural economy (slavery) was extirpated, put the region as a whole was on its heels. It was only until the latter half of the 20th century that the American South gained an equal economic footing with the rest of the United States.
Racism, whether overt or subtle, in America in general, but the South in particular, is a uniquely American economic poison that has held back the fortunes of this country in the past. Indeed, it’s continues to hinder economic progress and justice to this day in the United States.
Step-by-step explanation: