The group of mountains of which a brief account is given in this paper form one of the detached mountain groups lying east of the Rocky Mountain Cordilleras and rising abruptly from the level plains of central Montana. A glance at the map of the state shows the Missouri river, born of the Jefferson, Madison and Gallatin, in the mountain-encircled Gallatin valley, cutting its way in a general northward course through the outer ranges of the Rocky mountains until it debouches on the great open plains of the northwest. From here it turns in a rude arc, flowing eastward over the cataracts which have given rise and name to the city of Great Falls, and past Fort Benton, the head of steamboat navigation. In this arc, between the Missouri and the Little Belts, a front range of the Rocky mountains, the Highwood . . .