What is a short summary of Part I in the nonfiction book, The Warmth of Other Suns?

Part One, “In the Land of the Forefathers” introduces the three migrants that the story focuses upon, Ida Mae Gladney, George Starling and Pershing Foster. Wilkerson also describes her personal connection to the Great Migration. Her grandmother was among the six million black who fled the Deep South to escape the oppression that existed there.