THE SIERRA NEVADA DEFINES the interior of California in a way that overwhelms all other topographic features. The "great snowy mountain range" takes its name from the description offered by a Spanish explorer in 1776. Missionary Pedro Font first saw the snowy mountains, "una gran sierra nevada," from the low hills that separate San Francisco Bay from the Great Central Valley of California. His vista disclosed the central portion of the range—the area that in 1848 would become the focus of the gold rush which began the modern history of California. Altogether the Sierra is nearly 400 miles long with the northern end of the range often defined as Lake Almanor, near Lassen Peak and the southern end at Tehachapi Pass. [1]

For the northern two-thirds of its length the Sierra has a striking consistency. The crest is consistently very far east of the center of the range, and long river canyons drain the deeply eroded, but relatively gentle, western slope. North of Yosemite National Park, which is near the midpoint of the range, only a small part of the Sierra is above timberline. From Yosemite south, however, the range is higher and more rugged. Starting at Mt. Dana, just south of Yosemite's Tioga Pass, and continuing south for more than a hundred air miles, the crest consists of continuous high sharp peaks, each succesively more rugged. The ultimate summits of the Sierra rise near the southern end of this high, barren land, in the headwaters of the Kings and Kern rivers.

Despite the increasing heights of the ridges, the Sierra Nevada retains its westerly trending drainage pattern as far south as the Kings River canyons. The two major forks of the Kings River are born on summit peaks very near the eastern edge of the mountains and flow through long deep canyons down the west side of the mountains to the San Joaquin Valley. In the region of the Kaweah and Kern rivers, however, the shape and texture of the Sierra change radically. South of the Kings River, the Sierra Nevada has a double crest. The main crest, and home of the highest peaks in the range, remains far to the east, but a second, parallel, crest appears—the Great Western Divide. West of the divide the five forks of the Kaweah River drop steeply into the San Joaquin Valley. East of the Great Western Divide, but still west of the Sierran crest, is the fifteen-mile-wide canyon complex of the Kern River, draining not west, like every other Sierran river, but instead south for many miles, and finally, even reluctantly, west into the extreme southern end of the San Joaquin Valley.

These two factors—the presence of the highest peaks in the Sierra, and the well-spaced double crest with extensive uplands between—make the southern Sierra very different from the remainder of the range. Nowhere else is the Sierra so high. Nowhere else are the canyons so rugged and deep. And nowhere else does the Sierra rise so steeply from the west. The peaks of the Great Western Divide are much closer to the floor of the Great Central Valley than any other alpine area in the range. At the headwaters of the Middle Fork of the Kaweah River, summits over 12,000 feet high are less than thirty air miles from the nearly-sea-level valley floor. In the Yosemite and Tahoe regions the distance is much greater.

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