During her research for the book, Isabel Wilkerson interviewed more than 1,000 people who made the migration from the South to Northern and Western cities. Interestingly, many of the people who Wilkerson encountered — who moved during the time period of 1915 to 1970 — had no idea that they were even part of the Great Migration.
This relocation — called the Great Migration — resulted in massive demographic shifts across the United States. Between 1910 and 1930, cities such as New York, Chicago, Detroit and Cleveland saw their African-American populations grow by about 40 percent, and the number of African-Americans employed in industrial jobs nearly doubled.
“At the beginning of the 20th century, before the migration began, 90 percent of all African-Americans were living in the South. By the end of the Great Migration, nearly half of them were living outside the South in the great cities of the North and West. So when this migration began, you had a really small number of people who were living in the North and they were surviving as porters or domestics or preachers — some had risen to levels of professional jobs — but they were, in some ways, protected because they were so small.