Final answer:
Union General William Tecumseh Sherman set aside land in Georgia and South Carolina for settlement by former slaves through Special Field Orders, No. 15, after his March to the Sea.
Step-by-step explanation:
The states that Union General William Tecumseh Sherman set aside for settlement by former slaves were Georgia and South Carolina. Following his March to the Sea, which devastated Georgia and parts of South Carolina, Sherman issued Special Field Orders, No. 15.
This order specifically designated the Sea Islands along the Atlantic coast and a 30-mile inland stretch from Charleston, South Carolina, to Jacksonville, Florida, for the settlement of freed slaves. Approximately 400,000 acres were set aside, and the freedpeople were allocated forty-acre plots in what would become known as 'Sherman's Reserve'.