It is on the north line of the state, and thus shares the southern border of Canada opposite Saskatchewan.

[3] The majority of Fort Belknap Indian Reservation is located in the southeastern part of the county.

In terms of ancestry, 23.0% were German, 9.2% were Norwegian, 6.6% were Irish, 5.7% were English, and 2.0% were American.

After backing Theodore Roosevelt against Woodrow Wilson in the county's inaugural 1912 election, Blaine County has been won by the winner of the presidential election in every election except that of 1988, held during the aftermath of a major drought and farm crisis; Michael Dukakis won the county by 58 votes.

During two other drought years on the Great Plains, Adlai Stevenson II in 1956 and Gerald Ford in 1976 also came close to breaking the county's streak, losing by even smaller vote margins than George H. W. Bush.

[11] The main employers on the Reservation are the Gros Ventre and Assiniboine tribes.