Southwest of Denver, U.S. 285 climbs through the Front Range foothills and then drops into the North Fork Valley at Crow Hill. Resuming its climb to Kenosha Pass, the highway continues westward along the river, snaking between the high wall of the Platte River Mountains to the south and the Mt. Evans massif to the north.
At Kenosha Pass (elevation 10,000 feet), a scenic reststop offers a broad view of South Park, one of Colorado's large intermountain valleys. The north wall of the valley is formed by the Continental Divide as it curves to the west while the Mosquito Range, a southern extension of the Ten Mile Range rises along the Park's western edge; on clear days, the massive Sawatch Range, part of the Continental Divide, can be seen behind the Mosquito Range. The east side of South Park is formed by the Puma Hills, backed by the Tarryall Mountains and the southern rim, not readily seen from Kenosha Pass, is closed off by Thirty-nine Mile Mountain, part of a Tertiary volcanic field. The upper tributaries of the South Platte River rise along the Continental Divide and Mosquito Range, merging on the valley floor and flowing gradually to the southeast before cutting northeastward through the Front Range foothills.
Today, the mountain slopes were adorned with the gold of aspen groves and hazy sunshine warmed the air across the high altitude parkland, which has an average elevation of about 9200 feet. Circling counterclockwise, I crossed large cattle ranches along the northern part of the valley, passed through Fairplay and then angled southward on U.S. 285 along the Mosquito Range to the distinctive form of the Buffalo Peaks; unlike the rest of that range, which is composed of Precambrian granite, these twin peaks, visible throughout South Park, formed from Tertiary volcanic debris that collected within a basin, later lifted by tectonic forces and sculpted by Pleistocene mountain glaciers. Turning east on U.S. 24, I visited Antero Reservoir on the South Platte River, where Permian redbeds outcrop along its northern shore; out on the lake, flocks of American white pelicans, double-crested cormorants and rafts of mergansers prepared for migration. A detour south on Colorado 9 took me down to the Thirty-nine Mountain volcanic field, thought to be responsible for producing the Florissant Fossil Beds (to the northeast) about 35 million years ago. Returning to U.S. 24, I headed east and visited Eleven Mile Reservoir (also on the South Platte) where western grebes were abundant and especially vocal. Continuing east, I crossed the granite-lobed Puma Hills to Lake George and then followed Route 77 northwestward through the scenic Tarryall Creek Valley, gradually climbing between the Puma Hills and the imposing, rock-studded slopes of the Tarryall Range; joining the usual mix of mountain birds was a lone osprey, fishing along the Creek and seemingly out of place in that high, rugged landscape. Route 77 ends at Jefferson, on U.S. 285, completing my South Park road trip.
