The Moffat Tunnel finally provided Denver with a western link through the Continental Divide, as both Cheyenne, Wyoming, to the north and Pueblo to the south already enjoyed rail access to the West Coast.

It follows the right-of-way laid out by Moffat in 1902 while he was seeking a better and shorter route from Denver to Salt Lake City.

Provisions of the new lease forwent a monetary payment from UP in exchange for the right for the state to operate new passenger services over the line.

[5][6] Although its primary purpose today is as a rail route for coal and freight, and as a water tunnel from the Pacific watershed to the Denver area, it also sees use by Amtrak's California Zephyr and Winter Park Express.

[8] The tunnel was conceived by David Moffat of the Denver, Northwestern, and Pacific (DNW&P) railroad as early as 1902.

The original DNW&P tracks climbed Rollins Pass with a series of switchback loops with a steep 4% grade and severe snow conditions.

The issue was defeated in a court decision which ruled that Denver did not have the constitutional right to enter into a joint venture to construct the tunnel with a private corporation.

The Colorado Supreme Court in November 1922 upheld the constitutionality of the law creating the district and its ability to issue bonds.

It was finally disbanded after a series of political intrigues related to Winter Park Resort, which was built partly on land owned by the commission (known as the Evans Tract).

On September 11, 1996, owner Philip Anschutz sold the combined company to the Union Pacific Railroad in response to the earlier merger of the Burlington Northern and the Santa Fe which formed the Burlington Northern and Santa Fe Railway.

For many years, tunnel wastewater discharge, including coal dust and metal particles, has been a concern for Grand County and the Water Quality and Control Division of the Colorado Department of Public Health and Environment (CDPHE).

The pilot tunnel was officially "holed through" on February 18, 1927; the blast of dynamite was set off by President Calvin Coolidge pressing a key in Washington, D.C., and the program was broadcast by radio from the heart of the mountain.

Upon completion of the Dotsero Cutoff five years later, railroad connections through the tunnel shortened the distance between Denver and the Pacific coast by 176 miles (283 km).

By not changing 1927 to 1928 (the year the tunnel was actually finished and opened), this saved the commission $80 ($40 each portal) at the time (equivalent to $1,420 for both in 2023[17]).

[18] The project excavated 750,000 cubic yards (570,000 m3), or 3,000,000,000 pounds (1,400,000 t) of rock, equal to 1,600 freight trains of 40 cars each.

This decision was prompted by the corrosive effect of coal smoke and steam condensate, captive within the tunnel, on the joints.