DESCRIPTION OF THE PHILIPSBURG QUADRANGLE. By F. C. Calkins and W. H. Emmons.i INTRODUCTION. PHYSICAL FEATURES OF THE REGION. mountain canyons by their relative persistence, straightness, and breadth. One of these depressions, the Purcell Trench, has POSITION AND AREA. RELATIONS OF THE QUADRANGLE. already been mentioned as constituting part of the western The Philipsburg quadrangle is bounded by parallels 46° and In its general geographic and geologic relations the Philips­ boundary of the Rocky Mountains. Within the main body of 46° 30' and by meridians 113° and 113° 30' and covers 827.42 burg quadrangle forms a part of the Rocky Mountain the mountains there are other tracts, trending northwestward, square miles. It is in central-western Montana, not far from province, which lies between the Great Plains on the east and which afforded routes for the transcontinental railways. One the State boundary (see fig. 1), and includes parts of Granite the Great Basin, Columbia Plateau, and Northern Interior of the longest extends from Spokane, Wash., nearly to Deer- Plateaus on the west, and extends from northern New Mexico lodge, Mont., a distance of 300 miles. Its western part is 114° 112° 113 northward into Canada. That part of the province in and occupied by Coeur d'Alene River and its central and eastern adjacent to western Montana, including the region immedi­ parts mainly by Clark Fork of the Columbia. Another depres­ ately about the quadrangle, is characterized by certain general sion that has nearly the same direction, extending from Lake stratigraphic, structural, and topographic features, which give Pend Oreille southeastward for about 150 miles, is occupied by it some measure of geologic and physiographic unity. The a stretch of Clark Fork and by the lower part of Flathead quadrangle lies on the boundary between an area of relatively River. But the most remarkable is that which Daly calls the simple geology and uniformly mountainous topography at the Rocky Mountain Trench. It extends in a direction somewhat west and one of more complex geology and more diversified east of south from a point more than 200 miles north of the topography at the east, and it illustrates the features of both international boundary to a point near Kalispel, about 50 miles regions with a fullness that could be equaled in few other areas south of that boundary, where it divides into two branches, of equal size. either of which may be regarded as its chief southerly prolonga­ A brief description of the region that includes the quadrangle tion. The western branch, which is the broadest depression in will be given as an introduction to the more detailed description this part of the Rocky Mountains, extends due south and is of the quadrangle itself. A generalized map of the region forms occupied by Flathead Lake and by Bitterroot River and some figure 2. smaller streams. The eastern one, though narrower, lies more RELIEF. directly in line with the Canadian part of the trench. Its northern part is occupied by Swan River, and a more south­ 45° The term Rocky Mountains is applied, according to the best erly part of it is constituted by the valley of North Fork of American usage, to a broad zone trending in general northwest the Big Blackfoot, which heads opposite the Swan. Though and southeast, whose prevailingly mountainous character is obscure and interrupted beyond this point the depression may 114 diversified by extensive tracts of lowland. It is almost a be traced still farther south, and the principal valley of the FIGURE 1. Index map of part of Montana. necessary consequence of this diversity that the boundaries of Philipsburg quadrangle may be regarded as a part of it. The location of the Philipsburg quadrangle (No. 196) is shown by the darker ruling. Published folios describing other quadrangles, indicated by lighter ruling, are the following: Nos. 1, the zone should not everywhere be well defined. In the region The highest and most picturesque mountains of the region Livingston; 84, Three Porks; 30, Yellowstone National Park; 38, Butte special; 65, Fort especially considered here the western boundary is-more definite are in Montana, on the east side of the depression occupied by Benton; 56, Little Belt Mountains. than the eastern. Between the forty-fifth and forty-seventh Flathead Lake. Here lie the Mission, Lewis, Clark, and other and Deer Lodge counties and a little of Powell County. The parallels the Rocky Mountains are bounded on the west by ranges, several of whose summits exceed 10,000 feet in height, town of Philipsburg, from which the quadrangle is named, is the great basaltic plateau that is drained by Columbia River. and whose crests have a rugged alpine character attesting the in the north-central part of the area, about 50 miles northwest Near the forty-fifth parallel the eastern edge of the plateau work of glaciers. Although most of the glaciers "have passed of Butte. swings westward and the boundary of the Rocky Mountains away, many yet remain, particularly in the area of the Glacier INDUSTRIES AND SETTLEMENTS. north of that latitude may be regarded as formed by a remark­ National Park, where their survival is more favored than in ably long and narrow intermontane depression, called by Daly the tract farther south, not only by their northerly situation The wealth of the Philipsburg district lies chiefly in its the Purcell Trench, which virtually meets the Columbia basalt but by the greater height of their crests. Of the mountains deposits of gold and silver ore, and mining is still its greatest plateau near the south end of Lake Coeur d'Alene, and ex­ farther west, the most lofty constitute the well-defined Sierra industry. Agriculture, however, supports much of the popu­ tends thence northward beyond the international boundary. which overlooks the Bitterroot Valley on the west and to which lation. Small herds of horses and cattle are grazed upon the The eastern boundary of the Rocky Mountains is commonly the name Bitterroot Range is restricted by Lindgren. It is hills, and considerable hay is grown in the valleys. The regarded as contiguous to the Great Plains, but on this side only by its dominating height, exceeding 10,000 feet for some climate is too cool for growing most fruits and vegetables and the main mountain system has many outliers, such as the peaks, and its rugged character that this range is marked off was formerly regarded as prohibiting the commercial produc­ Little Rockies, in northern Montana, and the Big Horn Moun­ from the mountains still farther west, above which it rises tion of any grain except rye, but it has recently been proved tains and the Black Hills, farther south. Apart from these, abruptly. A similar domination of its surroundings is shown possible to mature the hardier varieties of wheat. k the main mass of the Rockies in Montana has a far more in a minor degree by the central part of the Cabinet Range, Philipsburg, whose site was determined by its convenience as a definite eastern boundary at the north than at the south. The which lies between Clark Fork and Kootenai River in north­ receiving and distributing point for the mines of the Flint Creek southeastern part of the State is occupied in large part by ern Idaho. The highest peaks of this range are about 8,500 district, is the largest town in the quadrangle and is accredited ranges, such as the Little Belt, Big Belt, and Crazy Mountains, feet high and one or two small glaciers still linger here on by the census of 1910 with a population of 1,109. The only which are separated by broad valleys or even completely shady northern slopes. These especially lofty ranges occupy other post offices are at Cable and Flint. Some settlements, surrounded by lowlands. The region of broadly alternating but a rather small fraction of the entire region. Throughout notably Granite, formerly second to Philipsburg in importance, heights and lowlands is bounded on the north by a more con­ the remainder of the ar6a the ridges are for the most part from have shared in the decline of the mines upon which they tinuously mountainous mass, whose east front rises with strik­ 6,000 to 7,000 feet high, are not accented by many conspicu­ depended. ing boldness from a vast expanse of plain. Although the ous peaks, and in general views appear comparatively subdued. Philipsburg is connected with the transcontinental route of boundary between these two regions is not sharp the difference Viewed in detail, however, their higher crests, having been the Northern Pacific Railway by a spur 26 miles long, which in their topography is significant as an expression of geologic deeply chiseled by the extinct alpine glaciers, of which the follows Flint Creek and joins the main line at Drummond. A differences: the area of partly isolated ranges may be identified region once contained many hundreds, do not seem lacking-in spur of the Butte, Anaconda & Pacific Railway enters the in figure 2 as that in which the areal geology is relatively com­ picturesque and vigorous character. quadrangle from the southeast. At the time of the survey on plex; the more continuous highland area farther north and which this folio is based it was used solely for hauling rock west is occupied almost wholly by pre-Cambrian rocks. DRAINAGE. from the quarries at Browns, but it has recently been extended The more or less isolated ranges of southwestern Montana The drainage of the region goes partly to the Pacific and to Cable. have a dominant but not general northwestward trend. The partly to the Atlantic.