The Bureau of Indian Affairs, usually known as the Office of Indian Affairs, was established as a separate agency within the War Department in 1824. Congress established the position of Commissioner of Indian Affairs in 1832. The Office of Indian Affairs was transferred in 1849 to the newly created Department of the Interior, where it has remained. In 1947 the Office of Indian Affairs was renamed the Bureau of Indian Affairs.
This description, records of field jurisdictions commented on below, and a list of contents for each of the 14 rolls of microfilm from which these images were scanned, are included in the descriptive pamphlet for M208, published by NARA. It can be viewed or downloaded here.