There were two Blackfeet treaties with the United States.
Alternate Names / Alternate Spellings: Blackfoot, Blackfoot Nation, Bloods
Blackfoot is the correct spelling, as it is spelled in Canada. However, the US Government made a mistake and labeled members of the tribe on the US side of the border Blackfeet.
Blackfeet Treaties:
Treaty With The Blackfeet, 1855
Treaty With The Blackfeet Sioux, 1865