Denver South Park & Pacific Link #4 (down)
The company's main line was 3 ft (914 mm) narrow gauge and went from Union Station in Denver up the valley of the South Platte River to the town of South Platte, then followed the North Fork of the South Platte through Buffalo Creek and Bailey. West of Bailey the route along North Fork and through the north end of the Tarryall Mountains essentially followed the route of present-day U.S. Highway 285 to Como, where it branched northward (see below). From Como the main line traversed South Park to Garo, where a spur went northward to Fairplay and Alma. The main line continued south over Trout Creek Pass. On the western side of the pass, a small spur of the main connected to Buena Vista, then traversed the southern end of the Sawatch Range through the Alpine Tunnel to Pitkin and Gunnison. The distance along the main line from Denver to Gunnison was approximately 208 miles (335 km).
A principal branch of the main line north from Como went over Boreas Pass to Breckenridge, Dillon, Keystone, Frisco and Climax. This branch terminated at Leadville.
A small 7-mile (11 km) branch of the main line 9 miles (14 km) south of Denver connected to Morrison (this line was actually constructed first).
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 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.
A mining boom near Leadville resulted in a construction race between Denver, South Park and Pacific and Denver and Rio Grande Western 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.
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 1880–1881, 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 Denver, South Park, & Pacific built north of Gunnison up the Ohio Creek Drainage to the Castelton and Baldwin Areas. Then planning to cross over Kebler Pass to Delta, Grand Junction, and points west and south. Track was laid four miles (6.4 km) past the Baldwin Mine, and another eight miles (13 km) were graded, but after losing right of ways to Lake City, and the San Juan Mining District, no more construction would be done west.
The railroad went into receivership in May 1888. On July 17, 1889, the company was sold at foreclosure proceedings to the Denver, Leadville and Gunnison Railway, a new railroad which was formed to operate the DSP&P lines. The successor company went into receivership on August 4, 1894. The Colorado and Southern Railway, charted in 1898, took over the former DSP&P lines in January 1899. The Colorado and Southern started dismantling in 1910 with the closure of the Alpine Tunnel. In 1930, the C&S attempted to shut down the main line through the Platte Canyon, in cooperation with the Denver Board of Water Commissioners, who desired to build a dam in the canyon (See Waterton Canyon, CO). Nevertheless, the construction of modern roads in the Rockies led to a decrease in revenue and traffic. The last freight and passenger trains between Denver and Leadville operated in April 1937, and on April 10, 1937, the South Park Line officially closed down. The last regular freight train operated between Denver and Como on April 25. The last 3 ft (914 mm) narrow gauge section, between Leadville and Climax, was converted to standard gauge on August 25, 1943.
Alpine Tunnel is a 1,772 ft (540 m) narrow gauge railroad tunnel located east of Pitkin, Colorado on the former Denver, South Park and Pacific Railroad route from Denver to Gunnison. At an elevation of 11,523 feet (3,512 m), it was the first tunnel constructed through the Continental Divide in Colorado, and according to the U.S. Forest Service "remains the highest railroad tunnel and the longest narrow gauge tunnel in North America." However, it did not last long in service. Construction began in January 1880 and was scheduled to last for six months but instead dragged on until July 1882, and the line was abandoned in 1910 due to minor damage in the tunnel. Now the tunnel is sealed shut and the remaining trackbed serves as a trail for hikers and bicyclists.
Location of the tunnel portals and establishing a center line of the bore were completed in December 1879. Construction took place from 1880–1881, by Cummings & Co. Construction company, and the tunnel was "holed through" on July 26, 1881. This was the highest and most expensive tunnel built up until that time. It is more than two miles (3 km) above sea level, with its highest point at 11,523.7 feet (3,512.4 m). It is 500 feet (150 m) under Altman Pass, later to be renamed 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 DSP&P had anticipated boring the Alpine tunnel through solid rock, taking about 6 months to complete. In the event, the line of the tunnel was found to run primarily through loose rock and clay; this very unstable ground required substantial timbering. The additional work necessitated by the unexpected ground conditions was a major contributor to the 18 month construction time.
The tunnel was abandoned in 1910 by the Colorado & Southern due to minor damage in the interior. This was not considered to be worth repairing due to a lack of traffic, as the line failed to get much beyond Gunnison on the west side. The Gunnison Division of the Colorado & Southern was abandoned from St. Elmo on the east side of the pass to Quartz on the west side. The line from Quartz to Baldwin was given to the Denver & Rio Grande Western in exchange for some little used lines around Leadville.
Little remains of the station complex built by the railroad to service its trains and workers at this remote and inhospitable location. Volunteers have restored the railroad's 1883 Alpine Tunnel telegraph office and reconstructed the station platform, 120 feet (37 m) of rail track, a turntable and an outhouse. Only ruins remain of the section house and engine house, and other buildings and railroad infrastructure have disappeared. Volunteers work on restoration of the complex at least once a year.
The Alpine Tunnel Historic District was placed on the National Register of Historic Places in April 1996. It is typically open from July to September.