{{Use mdy dates|date=MarchJuly 20202024}}

| location = [[Colorado]], USAUS

| owner = State of Colorado

| operator = Union Pacific

The Moffat Tunnel finally provided Denver with a western link through the Continental Divide, as both [[Cheyenne, Wyoming]], to the north and [[Pueblo, Colorado|Pueblo]] to the south already enjoyed rail access to the [[West Coast of the United States|West Coast]]. It follows the [[right-of-way (transportation)|right-of-way]] laid out by Moffat in 1902 while he was seeking a better and shorter route from Denver to [[Salt Lake City]]. The Moffat Tunnel averages 15 trains per day.<ref name="douglasscolony">{{cite web| |url = https://douglasscolony.com/featured_projects/moffat-tunnel/| |title = Moffat Tunnel| |website = Douglass Colony| |date = 2015 }}</ref> The railroad and water tunnels parallel one another; the water tunnel delivers a portion of [[Denver Water|Denver's water supply]]. In 1979, the tunnel was designated as a [[National Historic Civil Engineering Landmark]] by the [[American Society of Civil Engineers]].<ref>{{cite magazine |last = Witcher |first = T.R. |date = October 2018 |title = Unanticipated Benefits: The Moffat Tunnel |magazine = Civil Engineering |publisher = American Society of Civil Engineers |page = 43 }}</ref>

{{as of|1989}}, the Moffat was the fourth-longest railroad tunnel in North America. It was the longest non-[[Railway electrification system|electrified]] tunnel until 1956, when electrification was removed from the [[Cascade Tunnel]]. The tunnel is single-tracked, so only one train is run through at a time<ref>https://rumble.com/vpps8r-view-of-moffat-tunnel-from-locomotive-car-of-train.html</ref>, usually with eastbound and westbound trains alternating. For safety reasons, passengers are asked to not move from one car to another while the train is in the tunnel.{{cn|date=September 2023}}

The tunnel is ventilated by massive fans operating after a train has exited the tunnel. The portals have doors which are shut before the fans are activated. Originally, trains would have to wait some 20–30 minutes before proceeding into the tunnel after the doors were re-opened. Today, a sensor system is employed to evaluate the clearance of diesel exhaust, which today can be less than 20 minutes for lighter trains.<ref>[{{cite web |url = https://www.american-rails.com/moffat.html |title = Moffatt Tunnel (Colorado): Ventilation, |website = American-Rails] }}</ref>

The tunnel was conceived by [[David Moffat]] of the [[Denver and Salt Lake Railway|Denver, Northwestern, and Pacific]] (DNW&P) railroad as early as 1902. The original DNW&P tracks climbed [[Rollins Pass]] with a series of switch backswitchback loops with a steep 4% grade and severe snow conditions. Snow removal on the original line made it unprofitable to operate.<ref>{{harvp|Bollinger|1994|pp= 78, 182, 210, 226}}.</ref>

Moffat was unable to raise sufficient funds to build the tunnel before he died in 1911,<ref name="Rails that climb">{{harvp|Bollinger|1994|p= 173}}.</ref> but the forces behind the tunnel continued, and in 1914 a Denver bond issue was approved, financing two thirds of the construction cost of the tunnel. 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.<ref>{{cite court|url=https://case.law/caselaw/?reporter=colo&volume=58&case=0001-01|litigants=Lord v. City & County of Denver|year=1914|court=Colo.|vol=143|opinion=284|reporter=P.}}</ref>

In 1920, a bill was introduced in the state legislature to build three tunnels under [[Monarch Pass]], [[Cumbres Pass]], and Rollins Pass (the Moffat Route). The various regions of the state could not come to agreement, partly because the southern and southwestern regions feared that Denver would gain a new advantage in commerce from the Moffat Route. Blocking this legislation would ultimately backfire when Denver was finally able to secure financing for its tunnel.

The Moffat Tunnel was cut under a shoulder of [[James Peak]]. A small pilot tunnel was bored parallel with and {{convert|75|ft|m}} south of the main tunnel to facilitate the work and was {{convert|8|ft|m|spell=in}} high and {{convert|8|ft|m|spell=in}} wide.<ref name="TUNNELLING THROUGH THE ROCKIES">{{cite news |url = http://nla.gov.au/nla.news-article87032091 |title = Tunnelling Through The Rockies |newspaper = The Bunbury Herald and Blackwood Express |date = February 15, 1924 |access-date = March 24, 2013 |page = 7 |via = National Library of Australia }}</ref><ref name="Winchester2000">{{cite book |first = John N. |last = Winchester |url = http://westernriversinstitute.org/wp-content/uploads/2012/12/USCID-Transmountain-Paper-.pdf |title = A Historical View: Transmountain Development in Colorado |year = 2000 |access-date = 10 August 10, 2015 |url-status = dead |archive-url = https://web.archive.org/web/20150807061159/http://westernriversinstitute.org/wp-content/uploads/2012/12/USCID-Transmountain-Paper-.pdf |archive-date = August 7, 2015-08-07 }}</ref> In 1925, bad rock at the west end of the tunnel delayed construction, and costs soared. The pilot tunnel was officially [[tunnel hole-through|"holed through"]] on February &nbsp;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. Three more bond issues were sold before the tunnel was completed.

The railroad tunnel was holed through on July &nbsp;7, 1927, and formally turned over to the lessee on February &nbsp;26, 1928. Upon completion of the [[Denver and Salt Lake Railway#Dotsero Cutoff|Dotsero Cutoff]] five years later, railroad connections through the tunnel shortened the distance between Denver and the Pacific coast by {{convert|176|mi}}. The tunnel took 48 months to bore; the average daily progress was {{convert|21|ft}}. The first train passed through the tunnel in February 1928.

Although the original cost of the tunnel was pegged at $6.62&nbsp;million, final assessments collected by the Moffat Tunnel district, including interest, were $23,972,843. The cost of the two tunnels was $15.6&nbsp;million (equivalent to ${{Format price|{{Inflation|US-GDP|15600000|1928}} }} adjusted forin {{inflation-year|US-GDP}}{{inflation-fn|USGDP}}), which is $475 per linear foot ($1,558 per linear meter). Each of the ornamental bronze characters on the east and west portals (entrances) of the tunnel cost $40 and a separate cast had to be made for each character. Further, on each portal are the dates: 1923 (when construction began) and 1927 (the year the tunnel was scheduled to be completed). 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 ${{formatprice|{{Inflation|US|80|1928}}}} for both adjusted forin {{inflation-year|US}}{{inflation-fn|US}}).<ref name="The Moffat Road">{{cite book harvp|last = Griswold |first = P.R. 1995|title p= The Moffat Road |page = 7 }}{{full citation needed|date= April 2017}}</ref> The project excavated {{convert|750000|cuyd}}, or {{convert|3000000000|lb|t}} of rock, equal to 1,600 freight trains of 40 cars each. During the five-year project, 28 people died, six in a single cave-in on July &nbsp;30, 1926.

Track rails in the tunnel, originally [[track (rail transport)#Jointed track|jointed]], were replaced in the 1930s with [[track (rail transport)#Continuous welded rail|continuous welded rail]], one of the earliest such installations in North America. This decision was prompted by the corrosive effect of coal smoke and steam condensate, captive within the tunnel, on the joints.<ref>{{cite magazine| |title = One Rail Instead of Many| |magazine = [[Trains (magazine)|Trains]]| |date = March 1942 }}</ref>

The pilot bore was leased to the [[Denver|City of Denver]] for use as a [[Water tunnel (physical infrastructure)|water tunnel]] to divert water east from the [[Colorado River#Watershed|Colorado River Basin]] under the [[Continental Divide of the Americas|Continental Divide]] to the urban areas of the eastern slope. The pilot bore was enlarged to a diameter of {{convert|10.5|ft|m}}, giving it a carrying capacity of {{convert|1280|cuft/s|m3/s}}, and water diversion began in 1936. In 1979, the water tunnel was sold by the [[Moffat Tunnel Improvement District]] to the city. Since the 1940s, the tunnel has also conveyed water for the city of [[Englewood, Colorado|Englewood]].<ref name="Winchester2000" />

On Thursday, January &nbsp;30, 2020, the five remaining East Portal Camp Cabins (located at the East Portal of the Moffat Tunnel adjacent to Rollins Pass) were classified by Colorado Preservation, Inc. as one of Colorado's Most Endangered Places.<ref>{{cite web| |url = https://www.westword.com/arts/colorado-endangered-places-lists-adds-four-more-historic-spots-11626505| |title = Four Historic Sites Join Colorado's Endangered Places List| |website = Westword| |date = January 31, 2020 }}</ref><ref>{{cite web| |url = http://coloradopreservation.org/2020-list-colorados-most-endangered-places/east-portal-moffat-tunnel/| |title = East Portal Camp Cabins| |website = Colorado Preservation }}</ref><ref>{{cite web| |url = http://coloradopreservation.org/2020-list-colorados-most-endangered-places/| |title = 2020 List – Colorado's Most Endangered Places| |website = Colorado Preservation | date = January 30, 2020 }}</ref><ref>{{cite web| |url = https://denver.cbslocal.com/video/4455914-east-portal-moffat-tunnel/| |title = East Portal Moffat Tunnel| |website = CBS4 Denver |date = February 20, 2020 |access-date = March 2, 2020 |archive-date = February 25, 2020 |archive-url = https://web.archive.org/web/20200225172559/https://denver.cbslocal.com/video/4455914-east-portal-moffat-tunnel/ |url-status = dead }}</ref> In the spring of 2023, the Gilpin County Historic Preservation Commission's Vice Chair, B. Travis Wright, nominated these cabins to become a Gilpin County local historic landmark. On June&nbsp;13, 2023, the designation of the East Portal Camp Cabins was unanimously approved for local landmark designation, by a vote of 3–0.<ref>{{cite web |url = https://www.themtnear.com/articles/east-portal-cabins-history-didnt-end-when-the-tunnel-opened/ |title = East Portal Cabins – history didn't end when the tunnel opened - the Mountain-Ear |date = June 11, 2023 }}</ref><ref>{{cite web |url = https://www.preserverollinspass.org/about-us/historic-preservation/east-portal-camp-cabins/east-portal-camp-cabins-gilpin-county-historic-landmark/ |title = East Portal Camp Cabins—Gilpin County Historic Landmark }}</ref>

* [[CascadeAlva B. Adams Tunnel]], aanother similartunnel andthat longercarries railroadwater tunnelacross inthe [[WashingtonContinental (state)]]Divide in Colorado

* [[Eisenhower Tunnel]], equivalent tunnel for road traffic, built 50 years later.

* {{cite book |title = Rails that Climb |last = Bollinger |first = Edward Taylor |publisher = Johnson Publishing Company |location = Boulder, COColorado |year = 1994 |isbn = 0-918654-29-7 }}

* {{cite book |title = The Moffat Tunnel: aA Brief History |last1 = Forrest |first1 = Kenton |last2 = Albi |first2 = Charles |name-list-style = amp |publisher = Colorado Railroad Museum |year = 1985 }}

* {{cite web |url = http://www.colorado.gov/dpa/doit/archives/moffat/ |title = The Moffat Tunnel Commission Collection at the Colorado State Archives |publisher = Colorado State Archives |access-date = 2010-10-October 19, 2010 }}