Statistics for occurrence #1 of “Montana” in alphabetic letter A, entry group 6, entry assiniboine-indians of Harper's Encyclopedia of United States History:

... as early as 1640. In 1871 the number of Assiniboines in the United States was estimated at 4.850, and in 1900 there were 1.316, nearly equally divided at the Fort Peck and Fort Belknap agencies in Montana .
...
Max. Freq. Min. Freq.
Entity Corpus Doc Corpus Doc  
† Montana (Montana, United States) 252 186 0 0 0 user votes
Montana (Arkansas, United States) 0 0 0 0 0 user votes
Montana (Bulgaria) 0 0 0 0 0 user votes
Montana (Kansas, United States) 0 0 0 0 0 user votes
Montana (New Jersey, United States) 0 0 0 0 0 user votes
Montana (Ohio, United States) 0 0 0 0 0 user votes
Montana (Switzerland) 0 0 0 0 0 user votes
Montana (West Virginia, United States) 0 0 0 0 0 user votes
Montana (Wisconsin, United States) 0 0 0 0 0 user votes

† This entity has been selected by the automated classifier as the most likely match in this context. It may or may not be the correct match.