In A People's History of the United States, why did the mass emigration by blacks from the South occur in the 1920's rather than the Reconstruction...

"Lincoln got the praise for freeing us, but did he do it? He gave us freedom without giving us any chance to live to ourselves and we still had to depend on the southern white man for work, food, and clothing, and he held us out of necessity and want in a state of servitude but little better than slavery."  Ex-slave Thomas Hall, Federal Writer's Project

The limitations for freed slaves after the Civil War is documented in Chapter Nine:  Slavery Without Submission, Emancipation Without Freedom. Although the Civil War provided African-Americans with the hope of freedom, the reality of the situation was that they were still bound to the land like serfs. Zinn outlines the limited autonomy of the freedman that was the actuality and he blames it on black codes.  Black codes were passed in all of the former Confederate states.  They limited the movement of black people and tied them to their former positions on the plantations.  Black laws provided for complete separation of the races.  There were black codes that actually stated freedmen could be placed in "forced apprenticeship" programs under certain circumstances.  Forced apprenticeship was tantamount to the chattel slavery that existed before the war.  Even if the freeman had the resources, education, and means for moving to the North, black codes made it legally impossible for them. Zinn also briefly mentions at the beginning of the paragraph that racist attitudes were also prevalent in the northern states, which would suggest that migrating north was not a viable option.