Uncle Jessie and his family were sharecroppers in Terry Mississippi.  The documentary describes some of their life stories

Excerpt from: Definition Sharecropping and Tenant Farming

Sharecropping emerged from the conflicting interests of former slaves and former slave plantation owners. For planters, it was a way to resume agricultural production, as large plantations were turned into individual family plots. For former slaves, it moved away from the gang labor system and freed them from the constant supervision of white overseers.
The sharecropping family farmed someone else's land. The landowner demanded around half of the crop yield (usually cotton) in exchange for rent. But because the landowner provided the sharecropper with seeds, beasts of burden, farm tools, housing, and food, he often claimed a larger share.
Sharecroppers rarely were able to work their way up to become landowners themselves and were stuck in a cycle of dependency. Since the landlord demanded payment immediately after crops were sold, this left the cropper with little cash. Furthermore, because the cropper had put up future crops for collateral, this bound him in debt to the local merchant. The inability of sharecroppers to grow their own food also made them dependent on the landlord or merchant for sustenance. And credit rates were always high in the mostly isolated and rural areas of the South where sharecropping predominated. Finally, if cotton prices were low--which they increasingly were throughout the late 19th century--the sharecropper started the next season already in debt. It was extremely difficult for a cropper to break out of this cycle of dependency.
A black sharecropper in Alabama put it this way: 'The colored folks stayed with the old boss man and farmed and worked on the plantations. They were still slaves, but they were free slaves.'
Although the majority of rural blacks were sharecroppers by 1900, there were actually more white sharecroppers than black. Sharecropping was indicative of the poverty of the South after the destruction of the Civil War.
sharecropping and tenant farming
PBS Sharecropping by Another Name

Uncle Jessie moved to Detroit in 1950.  This was during the times of the Great Migration North where many of the blacks living in the south came north for better jobs and living conditions. 
The Great Migration North excerpt:
The Great Migration was the mass movement of about five million southern blacks to the north and west between 1915 and 1960.  During the initial wave the majority of migrants moved to major northern cities such as Chicago, Illiniois, Detroit, Michigan, Pittsburgh, Pennsylvania, and New York, New York.  By World War II the migrants continued to move North but many of them headed west to Los Angeles, Oakland, San Francisco, California, Portland, Oregon, and Seattle, Washington. - See more at: http://www.blackpast.org/aah/great-migration-1915-1960#sthash.hxV8uYWk.dpuf