Between 1915 and 1970, more than 6 million African-Americans moved out of the South to cities across the Northeast, Midwest and West.

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.

"[The Great Migration] had such an effect on almost every aspect of our lives -- from the music that we listen to to the politics of our country to the ways the cities even look and feel, even today," says Isabel Wilkerson. "The suburbanization and the ghettos that were created as a result of the limits of where [African-Americans] could live in the North [still exist today.] And ... the South was forced to change, in part because they were losing such a large part of their workforce through the Great Migration."

Wilkerson, whose parents were part of the Great Migration, details the mass exodus of African-Americans in her new book, The Warmth of Other Suns. The book weaves together three narratives of ordinary people -- a sharecropper's wife, a surgeon and a farm worker -- making their way from the South to an uncertain future up North.

During her research for the book, 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.

"Sometimes they would even say, 'Well, I migrated from Texas to Los Angeles in 1947, would that mean that I was part of it?' And that would mean they were right smack in the middle of it. But they didn't see themselves as that, partly because these decisions were individual personal decisions," she explains. "And in some ways, to me, that's one of the inspiring and powerful things about the Great Migration itself. There was no leader, there was no one person who set the date who said, 'On this date, people will leave the South.' They left on their own accord for as many reasons as there are people who left. They made a choice that they were not going to live under the system into which they were born anymore and in some ways, it was the first step that the nation's servant class ever took without asking."

Isabel Wilkerson won the Pulitzer Prize in 1994 for her coverage as the Chicago bureau chief of The New York Times. She is a professor in the College of Communications at Boston University and has received the George S. Polk Award, a Guggenheim Fellowship and the Journalist of the Year Award from the National Association of Black Journalists.

On the Jim Crow laws in the South

"There were colored and white waiting rooms everywhere, from doctors offices to the bus stations. ... But there were actually colored windows at the post office in Pensacola, Fla. And there were white and colored telephone booths in Oklahoma. There were separate windows were white people and black people would go to get their license plates in Mississippi. And there were even separate tellers to make your deposits at the First National Bank in Atlanta. It was illegal for black people and white people to play checkers together in Birmingham. And there were even black and white Bibles to swear to tell the truth on in many parts of the South."

On resistance from Northern African-American communities to the Great Migration

"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. They did not pose any threat. There was a kind of alchemy or acceptance of that small minority of people in these cities. So when you had this great wave and flood of people coming in from the South, many of them untutored and unaware of the ways of the big cities, it was in some ways threatening to those who were already there because they feared the positions that they had worked so hard to achieve -- that was tenuous at best in these big cities -- and that's why there was a great deal of resistance."

On her parents' migration experience

"My parents absolutely did not think of themselves as part of the Great Migration. They knew they were part of a great wave. No one really talked about it in those terms or gave it a name. I grew up surrounded by people who were from North Carolina, South Carolina, Georgia -- all around me. My parents' friends were all from there. They socialized with people from there. They were quite ambitious and competitive among themselves, bragging about that they were going to put their child through Catholic school because that was going to give them a better chance at succeeding. My parents sent me to a school across town, an integrated school, where I had the chance to meet and grow up with people who were from other parts of the world. ... I remember feeling that I would never have anything to contribute on St. Patrick's Day. I couldn't tell the stories that they might have been telling about their forebears and I felt left out, and only when I got older, and began reporting from different cities outside of Washington ... there were people who migrated from parts of the South to Chicago and Detroit and Los Angeles and San Francisco. And I began to put these pieces together and it began to hit me that this was so much like the immigration experience of so many others."

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