Argentine Pass

Argentine Pass
Elevation 13,207 ft (4,025 m)[1]
Traversed by Unimproved road
Location Clear Creek / Summit counties, Colorado, U.S.
Range Front Range
Coordinates 39°37′31″N 105°46′57″W / 39.62528°N 105.78250°W / 39.62528; -105.78250Coordinates: 39°37′31″N 105°46′57″W / 39.62528°N 105.78250°W / 39.62528; -105.78250
Topo map USGS Grays Peak

Argentine Pass, elevation 13,207 ft (4,025 m), is a high mountain pass that crosses the Continental Divide in the Front Range of the Rocky Mountains of central Colorado in the United States. Argentine Pass is located on the crest of the Front Range along the boundary southwest of Georgetown and is the highest named vehicle-accessible pass in the state.

Some early references use other names for the pass. An 1867 description of the trip from Georgetown into the valley of the Snake River refers to it as Sanderson Pass.[2] An lithograph caption from 1869 calls it the Snake River Pass.[3]


Argentine Pass is 0.94 miles (1.5 km) north of Argentine Peak and 0.95 miles (1.54 km) southwest of Mount Edwards. To the east is the valley of Leavenworth Creek, a tributary that joins the South Clear Creek south of Georgetown. To the west is the Horseshoe Basin, a deep glacial cirque at the head of the Peru Creek, a tributary that joins the Snake River just north of Montezuma.

The continental divide at Argentine Pass serves as the boundary between Clear Creek and Summit counties.

The pass was formerly used by a toll road and stagecoach route. The trail on the west side of the pass is the remains of this road. To the east, the Argentine Central Railway ran from Georgetown to the pass from 1906 to 1918. The Jeep trail to the pass follows the grade of this abandoned railroad.


On Sept. 14, 1864, former provisional territorial governor Robert Steele, along with James Huff and Robert Layton discovered silver high on the slopes of McClellan Mountain, 1.85 mi (2.97 km) north of what we now call Argentine Pass.[4] The mountains of this region are predominantly granite and gneiss, with veins containing silver-rich galena and blende (sphalerite), as well as iron pyrite, cupriferous pyrite (chalcopyrite), and some tetrahedrite.[5] This was the first major discovery of silver ore in Colorado. They named the deposit the Belmont Lode (from the French for beautiful mountain), and the surrounding area came to be known as the Argentine mining district (from argentum, Latin for silver). The discovery led to the growth of Georgetown as an early center of the silver mining industry in Colorado, although development was slowed by a general ignorance of how to properly treat the ore, by the high cost of transportation from the mines, and by the climate at that altitude. Eventually, both sides of the pass were heavily mined, and the district was divided into the East Argentine and West Argentine Districts, divided by the pass.[6][7] Many remains of mining activity remain visible today.

Work began on a toll road over Argentine Pass in 1869; the toll was typically one dollar for a team and wagon. In 1883, the road was purchased by Clear Creek and Summit County as a public highway; in the same year, the Denver, South Park and Pacific Railroad reached Dillon, diverting most of the freight traffic from the toll road. The stagecoach fare from Georgetown to Chihuahua, 15 miles away by road over the pass, was $2.50 in 1885.[8] Under county management, the road was never well maintained, and it gradually became impassable to teams and wagons.[9] The town of Waldorf was established as a rest stop on the east side of the pass.

In 1875, the Hayden Survey reported the Argentine Pass wagon road to be the highest wagon road in Colorado; at the time, it was the primary route from Georgetown to the mining camps in the Blue River Valley (Breckenridge and Montezuma).[10]

Colorado Telephone laid the first telephone line across Argentine Pass in 1899; this was a twisted-pair line resting directly on the ground, but it was replaced a year later with submarine cable. The cable, which carried 6 toll lines required intensive maintenance and was entirely replaced 3 times before its use was abandoned in 1909. Conies (pikas) chewing on the line caused major damage, as did rock slides. From 1909 to 1916, twisted pair lines were used again, with annual replacement. Finally, in the summer of 1916, Mountain States Telephone & Telegraph Company installed a heavily engineered overhead line, hauling supplies by rail to Waldorf and then onward by pack train. This line, only 1.3 miles long, was built at over 7 times the cost per mile of a comparable line in more forgiving territory; the cost was justified because it was the only telephone connection from Denver to Leadville and the western half of the state.[11]

In mid 1909, the Central Colorado Power Co. began delivering power over the Shoshone Transmission Line from Glenwood Springs to Denver.[12] This three-phase 90 kV line was split into two parallel lines as much as a mile apart for the 3-mile segment that crossed Argentine Pass from below Waldorf on the east to Argentine on the west (both are ghost towns today).[13][14] As currently routed, this line crosses the continental divide 1.25 miles (2.02 km) south of Argentine Pass, just south of Argentine Peak.

The Vidler Tunnel under Argentine Pass began with the Horseshoe tunnel, a silver mine. Reese Vidler purchased the mine in 1902 with a plan to extend it under the continental divide as a railroad tunnel. Tunneling progressed about 700 feet from the west portal and 5110 feet from the east portal before work stopped in 1911 (after several changes in ownership). In 1952, Herbert Young purchased the unfinished tunnel, intending to develop it as a highway tunnel. The 1.4 mile tunnel was completed in 1969 as a water tunnel, and is currently owned by the City of Golden. In 2007, major repairs were completed to the east portal and the mined-out area of the Flossie Vein. This water diversion project has a capacity of 31.5 cubic feet per second (0.892m3/s) with an average annual diversion of around 650 acre-feet (800,000m3).[9][15][16]


The peak wind speed recorded at the pass as of 1912 was 165 miles per hour (265 km/h), at which point the measuring equipment was blown away. Temperatures as low as -59 °F (-51 °C) were recorded, along with snow drifts as deep as 30 feet (9 meters) and persisting until August. This climate data appears to have been taken by the builders of the Shoshone Transmission Line.[17]

The Road Today

Vehicle travel is only possible on the Georgetown side of the pass during the summer months by a four-wheel drive vehicle with high-clearance. The trail on the Horseshoe Basin side is only accessible by foot or by mountain bike. The pass is the highest point on the American Discovery Trail.


  1. "Argentine Pass". Geographic Names Information System. United States Geological Survey. Retrieved 2011-02-19.
  2. Over the Plains to Colorado, Harpers New Monthly Magazine, Vol XXXV, No. CCV (June 1867); pages 1-21, pages 13-15 discuss the trip over Sanderson Pass, which must be what is now known as Argentine Pass.
  3. Alfred e. Mathews, Grays Peak, Gems of Rocky Mountain Scenery, self published, New York, 1869; pages are not numbered.
  4. Aaron Frost, Clear Creek County, History of Clear Creek and Boulder Valley, Colorado, O.L. Baskin & Co., 1880; page 278.
  5. Josiah Spurr and George Garrey, Chapter II -- History and Production of Mines, Economic Geology of the Georgetown Quadrangle, Colorado, Government Printing Office, 1908; page 104 discusses the ore body, page 173 discusses the history of the ore discovery.
  6. Rossiter W. Raymond, Chapter VIII -- Colorado, Mining and Metallurgical Industry of the United States, J.B. Ford & Co, 1876; page 352.
  7. Edward L. Berthoud, On Rifts of Ice in the Rocks Near the Summit of Mt. McClellan, Colorado, and on the Different Limits of Vegetation on Adjoining Summits in the Territory, American Journal of Science and Arts, Vol. XI, No, LXII (Feb. 1876); page 108.
  8. Crofutt's Grip-sack Guide of Colorado Vol II, Overland Publishing, Omaha, 1885; page 81.
  9. 1 2 T. S. Lovering, Geology and Ore Deposits of the Montezuma Quadrangle, Colorado, Professional Paper 178, United States Geological Survey, 1935; page 66 discusses the history of the toll road, page 111 discusses the Vidler Tunnel.
  10. Gustavus R. Bechler, Geographical Report on the Middle and South Parks, Colorado, and Adjacent Country, Chapter I: The Crest of the Main Rocky Mountains from Latitude 40° 30’ to Tennessee Pass (130 Mi), Ninth Annual Report of the United States Geological and Geographical Survey of the Territories Embracing Colorado and parts of Adjacent Territories, Being a Report of Progress of the Exploration for the Year 1875, F. V. Hayden, ed., Government Printing Office, 1877; page 376.
  11. Philip H. Dexter, The Denver-Leadville Toll Line Via Argentine Pass, the Mountain States Monitor, Nov. 1917; page 2, with many illustrations.
  12. Charles W. Henderson, Chapter 7 -- Production, history and mine development, Geology and Ore Deposits of the Leadville Mining District, Colorado professional paper 148, government printing office, 1927; page 134.
  13. High-Tension Transmission Experience in Central Colorado, Electrical World, Vol. 58, No. 15 (Oct. 7, 1911); page 871.
  14. Re: Colorado Power Co., Decision No. 527 Public Utilities Reports 1922D, Public Utilities Reports Inc, 1922; page 809.
  15. John N. Winchester, A Historical View: Transmountain Development in Colorado, 2000; retrieved July, 2015.
  16. 2007 Vidler Tunnel Repairs: Flossie Vein Collapse Area and East Portal Rebuild; retrieved July, 2015.
  17. A 100,000-Volt Transmission on the Roof of the Continent, Electrical World, Vol. 59, No. 22 (June 1, 1912); page 1205.

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