Banding has been going on since at least 1803, when John James Audubon tied silver onto the legs of birds to see if they came back the following year. Banding is the practice of identifying birds to help learn more about them.
Banding is controlled in the US by the US Fish and Wildlife Service. Before someone can start banding birds, they need a permit both from that organization as well as from the state the person lives in. There are around 2,500 master banders in the US, and the total number of banded birds is around 40 million.