Lucin Cutoff And Great Salt Lake Causeway

Last revised: May 9, 2023

By: Adam Burns

Almost everyone knows something about the famous meeting at Promontory, Utah in May, 1869 between the Central Pacific and Union Pacific which completed the Transcontinental Railroad.

However, under one plan engineers had hoped to do so via a water level grade across the Great Salt Lake and bypass the steep, mountainous terrain northwest of the body of the water.

The CP, of course, became part of the Southern Pacific system and it was not until around 1900 that serious consideration and planning began for what became known as the Lucin Cutoff. This first engineering feat to span the lake was constructed with both rock fill and timber trestles. 

It remained in use until the 1950s when the SP decided a replacement structure was needed, the Great Salt Lake Causeway that did away with (mostly) trestles and instead was a earthen right-of-way that split the body of water into two sections. Despite sometimes a maintenance headache, it is still in use today by successor Union Pacific. 

A Southern Pacific company photo with 2-8-2 #3258 (MK-6) ahead of train #14, the westbound "Pacific Limited," crossing the original Lucin Cutoff over Utah's Great Salt Lake circa 1950s.


In an attempt to keep costs low and time short in rushing to complete the Transcontinental Railroad a low-grade line across the Great Salt Lake was shelved. This would require the Central Pacific to build a circuitous and steep route around the lake with grades peaking at 2.2%.

Beginning at Lucin the line headed northeast through the Promontory Mountains with much of the grading work to Promontory Summit carried out by Benson, Farr, & West.

After the ceremonies of May 10, 1869 interestingly the CP abandoned its grade that continued on from Promontory to Ogden in favor of the Union Pacific alignment.

In 1885 the CP became a part of the growing Southern Pacific system and through the end of the 19th century the original alignment from Ogden to Lucin, around the lake and a distance of 146 miles through mountains that rose 700 feet above the lake, was the main line to California.

Looking directly west across the Great Salt Lake in August, 1971 we see the Lucin Cutoff. The original grade ran straight ahead while the new alignment, which opened in 1959, splits away to the right. Since this photo was taken the original causeway has been entirely removed. Jack Boucher photo.


In 1899 plans finally commenced on a water level route that would directly span the lake to its north with Lucin as the western terminus of the old alignment.

The Ogden & Lucin Railroad was a paper company created for the express purpose of building the new Cutoff with work officially beginning in March of 1902. It is interesting that while the original route across the water is often thought of as an incredibly long trestle, this only constituted about 12 miles of the distance.

It was originally hoped that the route would be a causeway, similar to what was built later. However, construction techniques at the time, while advanced, were not able to stabilize the right-of-way, as it kept sinking below the water's surface.

As a result, engineers decided on a more conventional approach; long earthen approaches built of stone-fill with a wooden trestle in the center.

A ground-level view of the original (left) and current (right) Lucin Cutoffs taken in August, 1971 by Jack Boucher. The searchlight signals protected the original alignment, which has been entirely removed today.

From there the line clipped the southern edge of Promontory Point and then continued on through another short fill before exiting to the eastern shoreline.

The route was wide enough to accommodate two tracks and shaved off 43 miles of the original alignment as it was now only 103 miles between Ogden and Lucin. Interestingly, Salt Lake City officials had hoped to lure the railroad directly through their town.

However, this would have required an additional 70 miles of railroad to be constructed and the company did not see the need for such an expense.


In the end, the original Lucin cutoff cost $4.5 million to build and officially opened to all through traffic on January 1, 1905. Surprisingly, the SP still used the original line for several years after the new route was opened, naming it the Promontory Branch to serve remaining shippers and passengers.

A northwestward view of the original and current Lucin Cutoffs. Note that much of the original alignment was constructed using wood pilings, which was rapidly aging in the salty water. The new right-of-way was built entirely with fill. Jack Boucher photo.

After nearly 10 years of failed attempts the railroad was finally able to abandon much of the line after June, 1942 which consisted of about 55 miles of track. As for the Lucin Cutoff, its final chapters are being written following World War II.

The wooden trestle was showing considerable age by this time after five decades of constant use. It was becoming a bottleneck as trains were forced to crawl over the structure at only 15 mph as the structure swayed and buckled.

Age was not the only reason the SP was looking to update its cutoff. It was also worried about fire to the wooden supports and ties, whether through a natural occurrence or intentionally.

As such, in 1950 the company began primarily studies to construct a new alignment that would be a full length, earthen causeway built entirely of stone fill.

Map (1968)

Work on the Great Salt Lake Causeway began in 1955, contracted to the Morrison-Knudsen Company (today, well known for its work on locomotives).

To reduce costs the Southern Pacific elected to reuse the original eastern and western approaches with the primary work meant to replace the roughly 12 miles of trestle.

The new alignment would be about 1,500 feet to the north of the bridge and required nearly 30 feet of sediment from the lake's floor to be dredged to reach bedrock for the rock fill to sustain a solid foundation.

After four years of work the Great Salt Lake Causeway's right-of-way was completed on July 9, 1959 and turned over to the SP for final track laying and signaling. This took another month to finish and by late August trains were once again rolling across the lake.

The original trestle remained were it stood and its remnants can still be seen today. 

Another aerial view of the two alignments looking west. Far in the distance you can see where the new grade ties into the original. Jack Boucher photo.


In the mid-1980s a 300 foot trestle interestingly had to be reinstalled to allow for the lake to flow properly as the northern arm was several feet lower than its southern counterpart.

The 1980s also saw the causeway nearly swamped due to the lake's unpredictable water levels. It had to be closed several times because of washouts and cost the railroad $85 million in maintenance repairs during the decade.

Since that time, however, the lake has never flooded as heavily. Today, the Great Salt Lake Causeway remains an important artery in the Union Pacific's system (since its 1996 takeover of SP) despite the fact that it has a parallel route to Salt Lake City via the old Western Pacific alignment. 

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