[RobbyS]

It was done mainly by Sherman. Finding his army encumbered by tens of thousands of escaped slaves, he took plantations on the Georgia-South Carolina coast, and gave them to the slaves. But most of the slaves were unprovided for, and in truth many northerners were indifferent. , because they expected the blacks to die out without the institution of slavery to sustain them. The history of Reconstruction was largely a record of the progressive abandonment of blacks by the Yankees, because they were not about to restart the Civil War to prevent the majority whites from taking control again in their own country. Their main interest was keeping the blacks from migrating north and west.

[Sherman Logan]

Not mostly by Sherman. It was by commanders earlier in the war who occupied the coastal areas of GA and the Carolinas. Plantations in these areas were abandoned by their owners, leaving the slaves.

The Union commanders, quite logically, split up the abandoned land among the slaves so they could grow their own food.