<P> On January 13, 1952, 222 passengers and crew aboard a train became stranded about 17 miles (27 km) 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 . </P> <P> In the spring of 1868, the Sierra Nevada were finally "conquered" by the Central Pacific Railroad (CPRR), after almost five years of sustained construction effort, with the successful completion at Donner Pass of its 1,659 - foot (506 m) Tunnel #6 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 two "Chinese Walls" necessary to breach Donner Summit constituted the most difficult engineering and construction challenge of the original Sacramento - Ogden CPRR route . </P> <P> Principally designed and built under the personal, often on - site direction of CPRR's Chief Assistant Engineer, Lewis M. Clement (1837--1914), 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 flyover at 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 in the harsh Sierra winters than the Track 1 tunnels and snow sheds over the summit . </P> <P> 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 fully 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 lineal feet of tunnel clearances in 15 restricted tunnels between Rocklin and Truckee and upgrading 30 miles of signals to CTC, although the original Donner Pass grade (Track 1) was not restored . Since then trains of full - height (20 ft 2 inch) 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 . </P>

When did central pacific railroad trains first pass over donner summit