Blasting Through The Summit At Donner Pass

At an elevation of 7,042 feet, just three miles west of Donner Lake, the Central Pacific Railroad faced its most formidable challenge: drilling a tunnel straight through the granite spine of the Sierra Nevada at Donner Pass. This wasn’t just any mountain crossing—it was hallowed and haunted ground. In the brutal winter of 1846–47, the Donner Party had become trapped in these very mountains. Dozens perished in the snowbound camps along the lake’s edge, some resorting to cannibalism in a desperate bid to survive. Now, just two decades later, railroad engineers aimed to blast a path through the same pass, turning a place of suffering into a corridor of speed and progress.

Central Pacific Railroad at Donner Lake, 1868.

The Summit Tunnel, 1,659 feet long and buried beneath 124 feet of solid granite, represented the highest and hardest point on the entire transcontinental route. Black powder wasn’t enough to pierce the unyielding rock. In early 1867, engineers turned to a far more dangerous option: nitroglycerin. Liquid, volatile, and shock-sensitive, it had never been used at this scale in America.

Clearing Summit Tunnel

Swedish chemist Alfred Nobel had already invented dynamite by this time—stabilizing nitroglycerin by absorbing it into an inert clay substrate—but that invention was still largely confined to Europe and had not yet reached the western United States. That meant the crews of the Central Pacific had to rely on raw, liquid nitroglycerin—far more powerful than black powder, but also vastly more unpredictable. It could detonate from the slightest shock, heat, or mishandling. But it worked—where black powder scraped out inches, nitroglycerin blew out feet. What had been expected to take more than two years was completed in less than a year. The risk was enormous, but the rewards were immense.

That risk fell hardest on the Chinese laborers who formed the backbone of the Central Pacific’s workforce. They chiseled and drilled through granite by candlelight, packed unstable explosives by hand, and hauled away the rubble. Many died in the process—killed by misfires, rockfalls, or suffocating fumes. Their names weren’t recorded, but their work shaped the mountain, the railroad, and America's future. They endured what the mountain had long denied: passage, and their labor made history.

A Chinese worker on the Central Pacific Railroad.

And then, on August 28, 1867, they broke through. The Summit Tunnel was complete. Just twenty-one years after members of the ill-fated Donner Party had spent five months trapped in the snowdrifts above Donner Lake, starving and dying in the shadow of these peaks, a passenger could now ride through the same mountains in a matter of minutes—warm, dry, and safe aboard a steam-powered train. It was more than a feat of engineering. It was a sign that the American West—and the very nature of travel itself—was changing faster than anyone could have imagined.

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 Hear how the Central Pacific conquered elevation, avalanche, and granite in the Sierra Nevada Mountains in Episode 2 of Legends of the Old West: Hell on Wheels - Mountains to Conquer: https://www.dimelibrary.com/post/part-2-transcontinental-railroad-mountains-to-conquer-legends-of-the-old-west