Front Range

Coordinates: 39°38′02″N 105°49′01″W / 39.63389°N 105.81694°W / 39.63389; -105.81694
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Front Range
Front Range Peaks in the Indian Peaks Wilderness
Highest point
PeakGrays Peak
Elevation14,278 ft (4,352 m)
Coordinates39°38′02″N 105°49′01″W / 39.63389°N 105.81694°W / 39.63389; -105.81694
The Front Range (excluding the Laramie Mountains) is shown highlighted on a map of the western U.S.
CountryUnited States
StatesColorado and Wyoming
Parent rangeRocky Mountains

The Front Range is a mountain range of the Southern Rocky Mountains of North America located in the central portion of the U.S. State of Colorado, and southeastern portion of the U.S. State of Wyoming.[1] It is the first mountain range encountered as one goes westbound along the 40th parallel north across the Great Plains of North America.

The Front Range runs north-south between Casper, Wyoming, and Pueblo, Colorado, and rises nearly 10,000 feet above the Great Plains. Longs Peak, Mount Blue Sky, and Pikes Peak are its most prominent peaks, visible from the Interstate 25 corridor. The area is a popular destination for mountain biking, hiking, climbing, and camping during the warmer months and for skiing and snowboarding during winter. Millions of years ago, the present-day Front Range was home to ancient mountain ranges, deserts, beaches, and even oceans.[2]

The name "Front Range" is also applied to the Front Range Urban Corridor, the populated region of Colorado and Wyoming just east of the mountain range and extending from Cheyenne, Wyoming south to Pueblo, Colorado. This urban corridor benefits from the weather-moderating effect of the Front Range mountains, which help block prevailing storms.


Pikes Peak and Garden of the Gods.
Uplifted Lyons Sandstone slabs along the eastern edge of the Front Range

Pikes Peak Granite[edit]

About 1 billion years ago, a mass of magma rose to the surface through a much older mantle, cooling to form what is now known as the Precambrian Pikes Peak Granite. Over the next 500 million years, the granite eroded with no sedimentation forming over this first uplift, resulting in a local expression of the Great Unconformity. At about 500–300 million years ago, the region began to sink and sediments began to deposit in the newly formed accommodation space. Eroded granite produced sand particles that began to form strata, layers of sediment, in the sinking basin. Sedimentation would continue to take place until about 300 million years ago.[2][3]

Fountain formation[edit]

Around 300 million years ago, the sinking suddenly reversed, and the sediment-covered granite began to uplift, giving rise to the Ancestral Rocky Mountains. Over the next 150 million years, during the uplift the mountains continued to erode and cover their flanks in their own sediment. Wind, gravity, rainwater, snow, and ice-melt supplied rivers that ultimately carved through the granite mountains and eventually led to their complete removal. The sediment from these mountains lies in the very red Fountain Formation today. Red Rocks Amphitheatre outside of Denver, Colorado, is set within the Fountain Formation.[2]

Lyons Sandstone[edit]

At 280 million years ago, sea levels were low and present-day Colorado was part of the super-continent Pangaea. Sand deserts covered most of the area, spreading as dunes seen in the rock record, known today as the Lyons Sandstone. These dunes appear to be cross-bedded and show various fossil footprints and leaf imprints in many of the strata making up the section.[2] Uplifted beds of Lyons Sandstone are found along the Front range and form the gateway to the Garden of the Gods.[3]

Lykins Formation[edit]

30 million years later, the sediment deposition was still taking place with the introduction of the Lykins Shale. This formation can be best attributed to its wavy layers of muddy limestone and signs of stromatolites that thrived in a tidal flat in present-day Colorado. 250 million years ago, the Ancestral Rockies were eroding away[3] while the shoreline was present during the break-up of Pangaea. This formation began right after Earth's largest extinction 251 million years ago at the PermianTriassic Boundary. Ninety percent of the planet's marine life became extinct and a great deal on land as well.[2]

Morrison Formation[edit]

After 100 million years of deposition, a new environment brought rise to a new formation, the sandstone Morrison Formation. The Morrison Formation contains some of the best fossils of the Late Jurassic. It is especially known for its sauropod tracks and sauropod bones, among other dinosaur fossils. As identified by the fossil record, the environment was filled with various types of vegetation such as ferns and Zamites.[2] While this time period boasts many types of plants, grass had not yet evolved.[2]

Dakota Sandstone[edit]

The Dakota Sandstone, which was deposited around 100 million years ago at the opening of the Cretaceous Western Interior Seaway from the Artic to the Tropics, shows evidence of ferns and dinosaur tracks. Sheets of ripple marks can be seen on some of the strata, confirming advancing and retreating near-shore environments.[2] These Dakota Group sandstone beds are resistant to erosion and have uplifted to form the Dakota Hogback, a ridge between the mountains and the plains.[3]

Benton Group / Niobrara Formation[edit]

Over the next 35 million years, the Cretaceous seaway repeatedly widened as far as Utah and Wisconsin and narrowed to near closure.[4] With no mountains present at the time, the Colorado area was in the line of the deepest channel of the seaway; but being on the Transcontinental Arch, the Front Range areas was relatively shallow and was near the last land to submerge as the seaway opened. Shale and chalk were deposited over the area as Greenhorn of the Benton Group and the Niobrara Formation. Within these beds are found abundant marine fossils (ammonites and skeletons of fish and such marine reptiles as mosasaurs, plesiosaurs, and extinct species of sea turtles) along with rare dinosaur and bird remains. Today, the Fort Hays Limestone member forms flatirons or secondary hogbacks on the east slope of the Dakota Hogback.[5]

Pierre Shale[edit]

The non-chalky shales of the Pierre Formation formed in the final cycle of the seaway. At about 68 million years ago, the Front Range began to rise again due to the Laramide Orogeny in the western half of the state, draining from being at the bottom of a sea to land again, giving yield to another fossiliferous rock layer, the Denver Formation.[2]

Denver Formation[edit]

Front Range near Estes Park, Colorado (Mummy Mountain)

The Denver Formation contains fossils of dinosaurs like Tyrannosaurus rex and Triceratops. While the forests of vegetation, dinosaurs, and other organisms thrived, their reign would come to an end at the Cretaceous–Paleogene boundary (which was formerly known as the K-T boundary). In an instant, millions of species were obliterated by a meteor impact in Mexico's Yucatán Peninsula. While this extinction led to the demise of the dinosaurs and other organisms, some life did prevail to repopulate the earth as it recovered from this tremendous disaster. The uplifted mountains continued to constantly erode and, by 40 million years ago, the region was once again buried in material eroded from the central mountains.[2]

Castle Rock Conglomerate[edit]

Suddenly, 37 million years ago, a great volcanic eruption took place in the Collegiate Range and covered the landscape in hot ash that instantly torched and consumed everything across the landscape. An entire lush environment was capped in a matter of minutes with 20 feet of extremely resistant rock, rhyolite. However, as seen before, life rebounds, and after a few million years mass floods cut through the rhyolite and eroded much of it as plants and animals began to recolonize the landscape. The mass flooding and erosion of the volcanic rock formed the Castle Rock Conglomerate that can be found in the Front Range.[2]

Quaternary deposits[edit]

Eventually, at about 10 million years ago, the Front Range began to rise up again and the resistant granite in the heart of the mountains thrust upwards and stood tall, while the weaker sediments deposited above it eroded away. As the Front Range rose, streams and recent (16,000 years ago) glaciations during the Quaternary age literally unburied the range by cutting through the weaker sediment and giving rise to the granitic peaks present today.[2] This was the last step in forming the present-day geologic sequence and history of today's Front Range.[2]

The Front Range as viewed from Greenwood Village south of Denver, Mount Blue Sky is on the far right, in the clouds.

Prominent peaks[edit]

The Front Range includes the highest peaks along the eastern edge of the Rockies. The highest mountain peak in the Front Range is Grays Peak. Other notable mountains include Torreys Peak, Mount Blue Sky, Longs Peak, Pikes Peak, and Mount Bierstadt.

Longs Peak
Pikes Peak
Mount Blue Sky
The 20 Mountain Peaks of the Front Range With At Least 500 Meters of Topographic Prominence
Rank Mountain Peak Subrange Elevation Prominence Isolation
1 Grays Peak[6] NGS Front Range 14,278 ft
4352 m
2,770 ft
844 m
25 mi
40.3 km
2 Mount Blue Sky NGS Front Range 14,265 ft
4348 m
2,769 ft
844 m
9.79 mi
15.76 km
3 Longs Peak NGS Front Range 14,259 ft
4346 m
2,940 ft
896 m
43.6 mi
70.2 km
4 Pikes Peak NGS Pikes Peak Massif 14,115 ft
4302 m
5,530 ft
1686 m
60.8 mi
97.8 km
5 Mount Silverheels NGS PB Front Range 13,829 ft
4215 m
2,283 ft
696 m
5.48 mi
8.82 km
6 Bald Mountain[7] PB Front Range 13,690 ft
4173 m
2,099 ft
640 m
7.51 mi
12.09 km
7 Bard Peak[7] PB Front Range 13,647 ft
4159 m
1,701 ft
518 m
5.43 mi
8.74 km
8 Hagues Peak NGS PB Mummy Range 13,573 ft
4137 m
2,420 ft
738 m
15.92 mi
25.6 km
9 North Arapaho Peak[7] PB Indian Peaks PB 13,508 ft
4117 m
1,665 ft
507 m
15.4 mi
24.8 km
10 Parry Peak[7] Front Range 13,397 ft
4083 m
1,731 ft
528 m
9.46 mi
15.22 km
11 Mount Richthofen[7] PB Front Range 12,945 ft
3946 m
2,680 ft
817 m
9.66 mi
15.54 km
12 Specimen Mountain[7] PB Front Range 12,494 ft
3808 m
1,731 ft
528 m
4.86 mi
7.82 km
13 Bison Peak NGS PB Tarryall Mountains PB 12,432 ft
3789 m
2,451 ft
747 m
19.14 mi
30.8 km
14 Waugh Mountain[7] PB South Park Hills PB 11,716 ft
3571 m
2,330 ft
710 m
20 mi
32.2 km
15 Black Mountain NGS PB South Park Hills PB 11,649 ft
3551 m
2,234 ft
681 m
8.03 mi
12.92 km
16 Williams Peak NGS PB South Williams Fork Mountains PB 11,620 ft
3542 m
2,049 ft
625 m
10.79 mi
17.37 km
17 Puma Peak[7] PB South Park Hills PB 11,575 ft
3528 m
2,260 ft
689 m
7.44 mi
11.97 km
18 Thirtynine Mile Mountain[7] PB South Park Hills PB 11,553 ft
3521 m
2,088 ft
636 m
10.61 mi
17.08 km
19 Twin Sisters Peaks[7] PB Front Range 11,433 ft
3485 m
2,328 ft
710 m
4.36 mi
7.01 km
20 South Bald Mountain [1] Laramie Mountains 11,007 ft
3355 m
1,844 ft
562 m
13.66 mi
22 km


The main interstate highways that run through the Front Range are Interstate 70, which crosses west of Denver, Colorado, and Interstate 80, which crosses near Laramie, Wyoming. U.S. Route 34 travels through the mountains near Loveland, Colorado, although this route is typically closed from October to May.[8] U.S. Route 24 travels through the southern Front Range west of Colorado Springs, eventually connecting with I-70 west of Vail, Colorado.

Along with the roads that run through the Front Range, the Union Pacific Railroad operates two rail lines through the mountains. The first Overland Route, transiting southern Wyoming, runs parallel to I-80 for much of its way. The second is the former Denver & Rio Grande Western Railroad Moffat Route, which runs parallel to the Colorado River and through the 6.5-mile-long Moffat Tunnel. Originally the Denver and Salt Lake Railway, the former Rio Grande is used for freight by both Union Pacific and BNSF, and it is also used by Amtrak's California Zephyr and Winter Park Express.

See also[edit]


  1. ^ "GNIS Feature Search". Archived from the original on 2012-07-14. Retrieved 2010-05-13. | U.S. Geological Survey confirms that the Laramie Mountains(range) are the northern extent of the Front Range.
  2. ^ a b c d e f g h i j k l m Johnson, Kirk R.; et al. (2006). Ancient Denvers. Fulcrum Publishing. ISBN 978-1-55591-554-4.
  3. ^ a b c d Williams, Felice; Chronic, Halka (2014) [1980]. Roadside Geology of Colorado (3rd ed.). pp. 9–11, 46–49. ISBN 978-0878426096.
  4. ^ R.J. Weimer (1984). J.S. Schlee (ed.). "Relation of unconformities, tectonics, and sea-level changes, Cretaceous of Western Interior, United States" (PDF). AAPG Memoir (Memoir 36, Interregional unconformities and hydrocarbon accumulation). American Association of Petroleum Geologists: 407. Retrieved March 21, 2021.
  5. ^ Marcus R. Ross, Liberty University, William A. Hoesch, Steven A. Austin, John H. Whitmore, Timothy L. Clarey (2010). "Garden of the Gods at Colorado Springs: Paleozoic and Mesozoic sedimentation and tectonics". Field Guide (18). The Geological Society of America: 77–93. Retrieved 2022-06-06.{{cite journal}}: CS1 maint: multiple names: authors list (link) (Benton Group is in current use in this location.)
  6. ^ The summit of Grays Peak is the highest point on the Continental Divide of North America.
  7. ^ a b c d e f g h i j The elevation of this summit has been converted from the National Geodetic Vertical Datum of 1929 (NGVD 29) to the North American Vertical Datum of 1988 (NAVD 88). National Geodetic Survey Archived 2011-10-19 at the Wayback Machine
  8. ^ "Road Status Report - Rocky Mountain National Park (U.S. National Park Service)". Archived from the original on 8 February 2019. Retrieved 8 January 2020.

Further reading[edit]

  • Fishman, N.S. et al. (2005). Principal areas of oil, natural gas, and coal production in the northern part of the Front Range, Colorado. Geologic Investigations Series I-2750-B. Reston, Virginia: U.S. Department of the Interior, U.S. Geological Survey.
  • Sprague, L.A., R.E. Zuellig, and J.A. Dupree. (2006). Effects of urban development on stream ecosystems along the Front Range of the Rocky Mountains, Colorado and Wyoming. USGS Fact Sheet 2006-3083. Reston, Virginia: U.S. Department of the Interior, U.S. Geological Survey.

External links[edit]