The state, including Puget Sound and other inland waters, is nearly rectangular in shape and is 69,127 square miles in area. Its western boundary is the Pacific Ocean. Politically, it is bounded on the north by the United States-Canadian Boundary (49° north lat.), on the east by the state of Idaho, and on the south by the state of Oregon. The Cascade Mountain Range, or Cascade Mountains Province, runs from the northern to the southern boundary and divides the state into two sections, of which the eastern is slightly the larger. The mountain range trends approximately 10° east of north and continues uninterruptedly into British Columbia, but on the south the Columbia River separates the Washington Cascades from the Cascades of Oregon. Near the northern border of the state the range is wide, extending from the Mount Baker Range on the west to Mount Chopaka, 100 miles to the east. In the central part of the state it is more compact, being some 60 miles wide in the vicinity of Mount Rainier. Farther south it expands to approximately 100 miles. The Cascades of Washington possess five great volcanic cones. These are Mount Baker (10,750 feet elevation) on the north, Glacier Peak (10,436 feet) in the north-central part, Mount Rainier (14,408 feet) in the central area, and Mount Adams (12,326 feet) and Mount St. Helens (9,697 feet) on the south. Excluding these volcanic peaks, the crests of the Cascades have a relatively uniform level descending from an average of 8,000 feet at the north to 5,000 feet at the south. Ranges jutting southeastwardly from the north-central Cascades parallel elongate intermontane valleys. These include the Entiat and Wenatchee mountains. The latter range reaches the Columbia River and forms an important barrier to mammalian movements. There is an extensive area of anticlinal ridges extending from the southern Cascades to the Columbia River. This area includes the Horse Heaven and other hills. Most of it is drained by the Yakima River and is termed, in this report, the Yakima Valley Area. [Illustration: FIG. 1. Cascade Mountains at Canadian boundary, looking west along boundary trail. Monument 100 in foreground, headwaters of Ashnola River in broad valley at right. (Forest Service photo, No. 4328.)]