Riddle

[mommie0105]

Before states were states, there were territories. And one town seemed to end up in a lot of them. At one time it was considered to be in the Dakota Territory. Yet in some old books the town will be found in Idaho Territory. But when sticking to facts, it is true that is was even declared the capital of the Montana Territory and then ultimately found itself with the Treasure State's borders. Name this Montana town that has been dodging these fast-moving western boundaries over the years.