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UP - Summit Tunnel


West Portal Of Tunnel 3, Contextual View To North From Milepost 537.6, 210mm Lens. The Single-Lens Searchlight-Type Block Signals Are Southern Pacific Common Standard Signals, A Type In Use Since The 1920s. Many Of These Have Been Replaced System-Wid

Photo taken for the Historic American Engineering Record

View photos at Library of Congress

BH Photo #300688



The Southern Pacific Railroad Cascade Route, built as the Natron Cutoff between Black Butte, California and Natron, Oregon was one of a series of major rebuildings and realignments of the original Central Pacific Railroad. Begun in 1905 under railroad magnate E.H. Harriman to replace the original Central Pacific route over the Siskiyou Mountains into Oregon, the Natron Cutoff had to overcome both natural and political obstacles. Stalled by government anti-trust lawsuits against Harriman, by World War I and the ensuing federal takeover of the nation's railroads, the Natron Cutoff finally overcame the rugged Cascade Mountains of Oregon to reach completion in 1927, at an ultimate cost of nearly $40 million. For the purpose of the current project, the Natron Cutoff was found likely to be eligible for the National Register of Historic Places at the state level of significance under Criterion A for its significance in engineering, transportation history, and the economic history of central Oregon, and in the development of the West, and under criterion B for its association with E.H. Harriamn. The Natron Cutoff's period of significance is 1905 to 1945, from the beginning of construction in 1905, through the years of its role in the economic development of the central Oregon, to the conclusion of the railroad's achievements in World War II. Built in 1925, Tunnel 3 is a contributive element of this property.

Tunnel 3 is a 3,655-foot, single track concrete-lined railroad tunnel, with concrete portal faces and wingwalls. The tunnel is on a five degree left curve alignment, and carries the tracks of the Union Pacific Railroad's (formerly Southern Pacific) Cascade Route line over the summit of the Cascade Mountains beneath Pengra Pass near Odell Lake. The west portal of the tunnel is at elevation 5,050 feet in Klamath County, Oregon while the east portal lies in Lane County at an elevation of 4,800 feet.

-- Historic American Engineering Record


Tunnel on Union Pacific Railroad under Pengra Pass
Lane County, Oregon, and Klamath County, Oregon
Open to traffic
Built 1925
- Henry & McFee
- Central Pacific Railway (CPRR)
- Southern Pacific Railroad (SP)
- Union Pacific Railroad (UP)
Total length: 3,655.0 ft. (0.7 mi.)
Also called
Tunnel 3
Approximate latitude, longitude
+43.59757, -122.05379   (decimal degrees)
43°35'51" N, 122°03'14" W   (degrees°minutes'seconds")
Approximate UTM coordinates
10/576372/4827611 (zone/easting/northing)
Quadrangle map:
Willamette Pass
4800 ft. above sea level
Inventory number
BH 63544 (Bridgehunter.com ID)

Update Log 

  • October 11, 2014: Added by Dave King


  • Dave King - DKinghawkfan [at] hotmail [dot] com
  • HAER OR-92 - Southern Pacific Railroad Natron Cutoff, Tunnel 3, Milepost 537.77, Odell Lake, Klamath County, OR