Denver, South Park and Pacific Railroad

The company was incorporated in the Colorado Territory as the "Denver, South Park and Pacific Railway" on October 2, 1872, with 2.5 million dollars in capital. Less than a year later, on June 16, 1873, it was reorganized by John Evans as the "Denver, South Park and Pacific Railroad" with an increased capitalization of 3.5 million dollars. Construction from Denver to Morrison began in August, 1873, by the Denver Railway Association, following approval by Arapahoe county voters who passed a $300,000 bond issue. On June 20, 1874, the tracks reached Morrison, and on July 3, scheduled service began between Denver and Morrison, with two 2 round-trip mixed trains per day. This branch would provide a healthy income from the start, shipping stone, lumber, and coal from Mt. Carbon. However, the financial panic in 1873, precipitated by Jay Cooke & Co. of Philadelphia (financiers of the Northern Pacific Railroad), caused a reduction in traffic, resulting in reduced construction until 1876. During this period, the Denver, South Park and Pacific Railroad struggled to remain solvent.

The tracks reached the mouth of the Platte Canyon on May 4, 1878, 20 miles (32 km) from Denver, and by June 2, the tracks reached 12 miles (19 km) up the canyon. The tracks reached Buffalo Creek on June 17. The following year, on May 19, 1879, the tracks reached to the summit of Kenosha Pass and on June 27 they reached Como. The original stone roundhouse at Como has been restored, and is presently in use in the operation of a 3’ narrow gauge locomotive acquired from the Klondike gold fields. An operating turntable has also been installed in the original turntable pit.

The railroad was earning about $1,200 a day, with only a daily operating expense of $480. This made the railroad very profitable, while also allowing a steady flow of money to help with construction cost. In November 1879, with the tracks only as far as South Park, the company contracted for the initial construction of the Alpine Tunnel, with an expected finish date of July 1, 1880. The following month, the tracks reached to the summit of Trout Creek Pass.

Leadville mining boom

A mining boom near Leadville resulted in a construction race between Denver, South Park and Pacific and

Denver and Rio Grande Railroad, with both reaching Buena Vista in early 1880. The Denver, South Park and Pacific completed construction first, but rather than both companies laying track to Leadville, Jay Gould pressured the two companies to make a deal called the "Joint Operation Agreement" of October 1, 1879. The companies agree that "...for the purpose of harmony and mutual profit...", the Denver and Rio Grande would lay tracks to the north from Buena Vista to the Leadville mining district, but that the Denver, South Park and Pacific would share equal traffic rights. Similarly, the Denver, South Park and Pacific would build into the Gunnison Country via Chalk Creek, with equal traffic rights given to the Denver and Rio Grande. In 1884 the D&RG ended the Joint Agreement, which forced the DSP&P to build their own line to Leadville. This route, the "High Line" left the original route at Como, and proceeded across Boreas Pass to Breckenridge, then across Fremont Pass to Leadville. This route was noteworthy for crossing the Continental Divide twice (from the Atlantic side to the Pacific side at Boreas Pass, and back to the Atlantic side at Fremont Pass), and was extremely difficult to operate in winter.

The Alpine Tunnel

Meanwhile, construction continued from Buena Vista past Mount Princeton to what would become the Alpine Tunnel. The Alpine Tunnel was "holed through" on July 26, 1881. Location of the tunnel portals and establishing a center line of the bore were completed in December 1879. Construction of the Alpine Tunnel took place between 1880 and 1881, by Cummings & Co. Construction company. This was the highest and most expensive tunnel built up until that time. It exceeds two miles (3.2 km) above sea level, with its highest point at 11,523.7 feet (3,512.4 m). It is 500 feet (152 m) under Altman Pass, later to be named Alpine Pass to prevent confusion, with a 1,825-foot (556 m) bore. It took 18 months to complete, with most of the construction done during the winter months. The tunnel only had a thirty-year life span, with the last locomotive passing through the tunnel on November 10, 1910.

The line exited the west portal of the Alpine Tunnel, to Alpine Tunnel Station, the highest railroad station in the United States. There also was a turntable, water tank, and a two-story frame boarding house that replaced the stone boarding house and engine house, which burned down in 1906. Parlin, located at milepost 189.78 is where the tracks of the Denver, South Park and Pacific and the Denver and Rio Grande joined up and ran along each other to Gunnison. The land for the track was given to the railroad by local dairy rancher John Parlin around 1877, with the condition that the railroad would build a depot, and stop for at least five minutes so passengers could buy milk. The main line reached Gunnison the following year in 1882.

The Snowplow Trials

In March 1889, the Denver, South Park and Pacific purchased a Leslie-type rotary snowplow to help combat the heavy snowfall across the railroad. However, further problems would arise from the usage of the plow. This included issues with rocks, fallen trees, and other debris in the snow that would be carried with the snow, especially in events such as blizzards and avalanches. If the crews didn't watch out, the rotary snowplow would run into the debris, damaging the plowing wheel. Orange Jull, who had sold the design rights to the Leslie Brothers, invented another type of snowplow, the Jull Centrifugal Snow Excavator. It was predicted to solve the debris problem in snowplowing and had succeeded in testing on several railroads in the Eastern United States. The Union Pacific arranged a competition between the now-Denver, Leadville, and Gunnison's rotary and a Jull-type plow purchased for testing. From the 16th to the 18th of April, 1890, the two plows were tested in a series of trials, running from Hancock to the east portal of the Alpine Tunnel, but Jull's machine kept having issues, such as derailment or not properly clearing the snow. At last, the total failure of the snow excavator was acknowledged by its crew and Orange Jull, and the Leslie machine had come out victorious. Attendants included high-ranking officials from railroads across the United States and other figures such as photographer William Henry Jackson and author Cy Warman.