About 28 miles west of Metro Denver, U.S. 40 cuts northward from Interstate 70, climbing to Berthoud Pass on the Continental Divide. North of that pass, the highway descends into the valley of the Fraser River, a tributary of the Upper Colorado; the rivers merge in Granby, where the Colorado River flows in from the east and continues on to the west.
From Granby, eastbound U.S. 34 leads eastward and then northward through the Upper Colorado Valley, passing a scenic trio of lakes (Lake Granby, Shadow Mountain Lake and Grand Lake), all backed by the high peaks of the Front Range; the Colorado actually flows through Shadow Mountain Lake and Lake Granby. North of Grand Lake, U.S. 34 enters Rocky Mountain National Park and gradually climbs through the Kawuneeche Valley, the path of the Colorado's uppermost segment; tributaries from the Front Range (to the east) and the Never Summer Range (to the west) feed the main channel. The Colorado River Trail, which leads to the river's headwaters on the Continental Divide, is accessed from a trailhead lot off Trail Ridge Road (U.S. 34), just before the latter begins its climb to the alpine tundra.
Visiting the Kawuneeche Valley today, I hiked part of the Colorado River Trail and took a few side trails that lead down to the stream or into the valley meadows. By late summer, the Upper Colorado is but a small creek and it's difficult to associate this gentle, meandering stream with the river's raging torrent far to the southwest. Of course, many large tributaries merge with the Colorado along its course and the river carved its spectacular canyons primarily during the Pleistocene, a time when a cool, wet climate enveloped North America and when mountain glaciers filled the Kawuneeche Valley.
