Final answer:
The Freedmen's Bureau was the agency established by Congress in March 1865 to establish a working free labor system. It provided relief for loyal refugees and helped them transition to freedom after the Civil War.
Step-by-step explanation:
The agency established by Congress in March 1865 to attempt to establish a working free labor system was the Freedmen's Bureau. The Freedmen's Bureau, also known as the Bureau of Refugees, Freedmen, and Abandoned Lands, was created to provide relief for loyal refugees, both black and white, and help them transition to freedom after the Civil War. It administered by the War Department, distributed clothing, food, fuel, and land, and ran schools to prepare freedmen for citizenship.