What were the federal government's major challenges in reconstructing the South after the Civil War during the period from 1865 to 1877?

The South's economy was ravaged and bankrupt. It needed to be rebuilt. Slavery was going to end formally, but there was no clear plan how to integrate the freed 4 million black people into mainstream social and political life; besides, the southern states passed a series of laws that thwarthed personal development of former slaves and reduced them to dependence to the agrarian system of the South. Discrimination against African Americans continued. And a major challenge was how heal the wounds of war and forge a new sense of national unity.