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Donner Pass

Hidden Hills

January 11, 2023

Donner Pass is a 7,056-foot-high mountain pass in the northern Sierra Nevada, above Donner Lake and Donner Memorial State Park about 9 miles west of Truckee, California. Like the Sierra Nevada themselves, the pass has a steep approach from the east and a gradual approach from the west.

Location in CaliforniaThe pass has been used by the California Trail, First transcontinental railroad, Overland Route, Lincoln Highway and Victory Highway (both later U.S. Route 40 and still later Donner Pass Road), as well as indirectly by Interstate 80. The pass gets its name from the ill-fated Donner Party who overwintered there in 1846. Today the area is home to a thriving recreational community with several alpine lakes and ski resorts (Donner Ski Ranch, Boreal, and Sugar Bowl). The permanent communities in the area include Kingvale and Soda Springs, as well as the larger community below the pass surrounding Donner Lake.


To reach California from the east, pioneers had to get their wagons over the Sierra Nevada mountain range. In 1844 the Stephens-Townsend-Murphy Party followed the Truckee River into the mountains. At the head of what is now called Donner Lake, they found a low notch in the mountains and became the first overland settlers to use the pass. The pass was named after a later group of California-bound settlers. In early November 1846 the Donner Party found the route blocked by snow and was forced to spend the winter on the east side of the mountains. Of the 81 settlers, only 45 survived to reach California; some of them resorting to cannibalism to survive.

On January 13, 1952, 222 passengers and crew aboard a train became stranded about 17 miles west of Donner Pass at Yuba Pass, on Track #1 adjacent to Tunnel 35 (on Track #2), at about MP 176.5. Southern Pacific Railroad's passenger train City of San Francisco was en route westbound through the gap when a blizzard dumped so much snow the train was unable to move forward or reverse. The passengers and crew were stranded for three days until the nearby highway could be plowed sufficiently for a caravan of automobiles to carry them the few miles to Nyack Lodge.

Central Pacific Railroad

In the spring of 1868, the Sierra Nevada were finally "conquered" by the mainly Chinese laborers of the Central Pacific Railroad (CPRR), after almost three years of sustained drilling and blasting through granite, with the successful completion at Donner Pass of its 1,659-foot (506 m) Tunnel #6 (a.k.a. the Summit Tunnel) and associated grade, thus permitting the establishment of commercial transportation en masse of passengers and freight over the Sierra for the first time. Following a route first surveyed and proposed by CPRR's original Chief Engineer, Theodore D. Judah (1826–1863), the construction of the four tunnels, several miles of snowsheds, and a hand-crafted stone retaining wall 75-foot tall (a.k.a. Chinese or China Wall in recognition of the Chinese builders) necessary to breach Donner Summit[8] constituted the most difficult engineering and construction challenge of the original SacramentoOgden CPRR route.

CPRR Engineers L. M. Clement and T. D. Judah

Principally designed and built under the personal, often on-site direction of CPRR's Chief Assistant Engineer, Lewis M. Clement (1837–1914),[10] the original (Track 1) summit grade remained in daily use from June 18, 1868, when the first CPRR passenger train ran through the Summit Tunnel, until 1993 when the Southern Pacific Railroad(SP) (which operated the CPRR-built Oakland-Ogden line until its 1996 merger with the Union Pacific Railroad (UP)) abandoned the 6.7 mile (10.7 km) section of Track #1 over the summit running between the Norden complex (Shed 26, MP 192.1) and the covered crossovers in Shed #47 (MP 198.8), one mile east of the old flyoverat Eder. All traffic has since operated over the Track #2 grade crossing the summit 1 mile (1.6 km) south of Donner Pass through the 10,322-foot (3,146 m)-long Tunnel #41 running under Mount Judah between Soda Springs and Eder. SP made this change because the railroad considered Track 2 and Tunnel 41 (which was opened in 1925 when the summit section of the grade was finally double tracked) to be easier and less expensive to maintain during the harsh Sierra winters than the Track 1 tunnels and snow sheds over the summit.

In conjunction with major ongoing upgrades and expansions being made to the Port of Oakland in order to better accommodate the rapidly growing North American trade with Asia and the Pacific, the cooperation of UP, the Port's principal rail partner, has been sought to "construct a second track and raise tunnel clearances over Donner Pass for container trains linking California with the rest of the country." This would likely require either a new parallel tunnel next to Tunnel 41 or the replacement of the summit section of Track 1 between the Norden complex and Shed 47; either would increase capacity and effectively eliminate delays currently caused by having to run all east and west bound traffic between Norden and Shed 47 over a single track. (To eliminate bottleneck delays the now single track 7.1-mile (11.4 km) section between Switch 9 (MP 171.9) at Emigrant Gap and Shed 10 (MP 179.0) west of Cisco would likely also have to be restored to double track.) Improvements were completed on the Sierra grade in November 2009, including increasing 18,000 feet (5.5 km) of tunnel clearances in 15 restricted tunnels between Rocklin and Truckee and upgrading 30 miles (48 km) of signals to CTC, although the original Donner Pass grade (Track 1) was not restored. Since then trains of full-height or 20 feet 2 inches (6.15 m), double-stack container cars have run over Donner Pass; some tunnels on Track 2 between Bowman and Colfax were not enlarged, so stack trains in both directions must use the older, tunnel-free Track 1 between those points.

CPRR Tunnel #6 with Donner Lake in the distance and Donner Peak to rightRoute of the original CPRR grade at Donner Pass.

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