The Philipsburg quadrangle is bounded by parallels 46° and 46° 30' and meridians 113° and 113° 30'. Its length from north to south is 34.5 miles, its average width east and west 23.8 miles, and its area 827.42 square miles. As shown on the index map (fig. 1), it is not far
from the western border of Montana and nearly midway between the northern and southern boundaries of the State. The nearest large town is Anaconda, the site of the great smelter of the Amalgamated Copper Co., which is on Warm Spring Creek, a mile or two beyond the eastern
boundary of the quadrangle.
Philipsburg lies about midway between the eastern and western limits of the Rocky Mountain system, if the term be used in the broad sense prevailing in the United States. In the general latitude of Montana the system as defined by American usage is bounded on the west by the Columbia River basalt plain and on the east by the Great Plains. The western limit is fairly definite, but on the east there is no very definite line between the plains and mountains; the mountains are fairly continuous west and north of the Philipsburg quadrangle, but to the east and southeast mountains alternate with broad stretches of semiarid lowland. The quadrangle therefore overlaps the line between two physiographic provinces, one characterized by isolated mountain groups, of which the Flint Creek Range is the most westerly, and the other by more continuous elevations, of which the Sapphire Mountains are an example.
