Rising dramatically above the high desert and pine forests of northern Arizona, the San Francisco Peaks form one of the most recognizable mountain landscapes in the American Southwest. Their highest summit, Humphreys Peak, is the highest point in Arizona, reaching a current National Geodetic Survey elevation of approximately 12,637 feet (3,851.9 meters).
Although the individual summits can look like a compact mountain range, the San Francisco Peaks are actually the deeply eroded remains of one enormous stratovolcano known as San Francisco Mountain. Volcanic construction, collapse, erosion, glaciation, and weathering have transformed the ancient volcano into the collection of rugged peaks seen today.
The mountains are also much more than a geological landmark. They are sacred to numerous Indigenous peoples of the Southwest and remain an important cultural and spiritual landscape. At the same time, the high country provides some of Arizona’s most challenging hiking, alpine environments, skiing, and spectacular views.
⚡ Fast Facts
| Feature | Details |
|---|---|
| Continent | North America |
| Country | United States |
| State | Arizona |
| County/Region | Coconino County, northern Arizona |
| Mountain Group | San Francisco Peaks |
| Geologic Setting | San Francisco Volcanic Field, Colorado Plateau |
| Highest Point | Humphreys Peak |
| Elevation of Highest Point | 12,637 ft (3,851.9 m), current NGS NAVD 88 elevation |
| Prominence of Highest Point | About 6,042 ft (1,842 m) |
| Isolation of Highest Point | About 245.86 mi (395.67 km) |
| Nearest Higher Neighbor (NHN) | Burwell Peak, Colorado |
| Approximate Coordinates of Humphreys Peak | 35.34634° N, 111.67795° W |
| Protected Land | Coconino National Forest and Kachina Peaks Wilderness |
| Mountain Type | Eroded stratovolcano |
| Most Recent Known Eruptions of San Francisco Mountain | About 93,000 years ago |
Elevation note: Many maps, signs, publications, and older references give Humphreys Peak an elevation of 12,633 feet (3,850 meters). The National Geodetic Survey’s current data sheet for the FRISCO benchmark gives a NAVD 88 orthometric height of 12,637 feet (3,851.9 meters). Small differences among reputable databases therefore do not necessarily represent an error.
📍 Location and Geography
The San Francisco Peaks rise immediately north of Flagstaff, Arizona, where their high slopes dominate the northern horizon. Because Flagstaff itself lies at roughly 7,000 feet (2,134 meters), the region already has a considerably cooler climate than the low deserts surrounding Phoenix and central Arizona.
The Peaks stand along the southern margin of the Colorado Plateau, a vast elevated region covering portions of Arizona, Utah, Colorado, and New Mexico. They form the most prominent part of the San Francisco Volcanic Field, which encompasses roughly 1,800 square miles (4,700 square kilometers) of northern Arizona.
It is important to distinguish the San Francisco Peaks from the much larger volcanic field surrounding them. The San Francisco Peaks are the summit remnants of San Francisco Mountain, while the San Francisco Volcanic Field contains hundreds of separate volcanic features extending across the landscape.
More than 600 volcanoes have formed within the volcanic field during approximately the last six million years. These include lava domes, cinder cones, lava flows, and larger composite volcanoes.
🏔️ Major Peaks
Humphreys Peak is the best-known summit, but several substantial peaks encircle the high interior basin of the old volcano.
| Peak | Approximate Elevation |
|---|---|
| Humphreys Peak | 12,637 ft (3,851.9 m) NGS |
| Agassiz Peak | 12,359 ft (3,767 m) |
| Fremont Peak | 11,967 ft (3,648 m) |
| Aubineau Peak | 11,854 ft (3,613 m) |
| Rees Peak | 11,476 ft (3,498 m) |
| Doyle Peak | 11,465 ft (3,495 m) |
| Schultz Peak | 10,083 ft (3,073 m) |
Elevations for secondary summits vary slightly among modern topographic and peak databases, partly because of differing survey methods and definitions of the exact summit point.
Humphreys Peak is not only the highest of the San Francisco Peaks but also the highest natural point anywhere in Arizona. Its substantial topographic prominence makes the mountain massif especially noticeable when viewed from the surrounding plateau.
🪨 Geology and Volcanic History
The appearance of the San Francisco Peaks today is dramatically different from that of the original volcano.
San Francisco Mountain developed as a large stratovolcano, also known as a composite volcano. Such volcanoes grow through repeated eruptions that produce layers of lava, ash, and other volcanic material.
According to the U.S. Geological Survey, construction of San Francisco Mountain occurred approximately between one million and 93,000 years ago. The volcano was therefore active during a relatively late portion of the much longer history of the San Francisco Volcanic Field.
Scientists estimate that the original volcano may once have risen to roughly 15,000–16,000 feet (4,570–4,880 meters). If so, its original summit stood thousands of feet higher than present-day Humphreys Peak.
The upper part of the volcano was eventually profoundly altered. Large-scale slope failure, erosion, and subsequent glacial activity helped create the open, rugged form visible today. The eastern to northeastern side of the old volcanic edifice is breached, exposing the broad Inner Basin surrounded by the surviving high peaks.
During the Pleistocene ice ages, glaciers occupied portions of the high mountain. Moving ice carved valleys and redistributed enormous quantities of rock and sediment. Glacial landforms are therefore another important part of the San Francisco Peaks’ modern landscape.
The surrounding volcanic field continued producing eruptions long after activity ceased at San Francisco Mountain itself. This distinction is important: the ancient San Francisco Mountain has not erupted for roughly 93,000 years, while volcanism elsewhere in the broader field continued much more recently.
🌲 Forests and Alpine Ecosystems
One of the most remarkable characteristics of the San Francisco Peaks is the enormous change in vegetation between their lower and upper slopes.
Ponderosa pine forests dominate much of the country around Flagstaff. With increasing elevation, the forest composition shifts through mixed-conifer and subalpine communities. Aspen groves add brilliant yellow color to portions of the mountain during autumn, while spruce and fir become increasingly important at higher elevations.
Near the highest summits, the environment changes dramatically again.
The San Francisco Peaks contain Arizona’s only true alpine tundra zone. Above the upper tree line, plants must survive intense sunlight, strong winds, freezing temperatures, heavy snow, short growing seasons, and relatively thin soils.
Among the most important plants found here is San Francisco Peaks ragwort (Packera franciscana), a small alpine plant found naturally nowhere else on Earth. Its entire native range is confined to high-elevation talus habitat on the San Francisco Peaks. The plant is federally listed as threatened.
The combination of elevation and ecological isolation makes the upper mountain unusually important for biological conservation.
Wildlife inhabiting the broader forested mountain landscape includes elk, mule deer, black bears, squirrels, numerous bird species, and other animals associated with northern Arizona’s montane forests.
🏛️ Cultural and Spiritual Importance
The San Francisco Peaks have profound cultural significance that long predates their modern English name.
Numerous Indigenous nations regard the mountains as sacred, including the Hopi, Navajo, Havasupai, Zuni, Hualapai, Apache, Southern Paiute, Yavapai, Acoma, and others. Different communities have their own traditional names, histories, ceremonies, and relationships with the mountains.
For example, the mountains are known as Dook’o’oosłííd in Navajo tradition and Nuva’tukya’ovi in Hopi tradition. They should therefore be understood not merely as archaeological or historical cultural sites but as part of a living sacred landscape that remains important today.
The modern Spanish-derived name dates to the early colonial period. Franciscan missionaries applied the name San Francisco to the mountain in the 17th century in honor of Saint Francis of Assisi.
Humphreys Peak received its present English name in the 19th century. Geologist Grove Karl Gilbert named it in 1873 for Andrew Atkinson Humphreys, a U.S. Army officer and engineer.
Visitors should respect both the physical environment and the continuing cultural importance of the Peaks.
🥾 Hiking and Climbing Routes
The San Francisco Peaks offer some of Arizona’s finest high-elevation hiking, but their altitude, weather, snow, and rugged terrain deserve serious respect.
Humphreys Trail
The most popular route to Arizona’s highest point is the Humphreys Trail No. 151.
The Forest Service lists the trail at approximately 4.8 miles (7.7 kilometers) one way, resulting in a summit outing of roughly 9.6 miles (15.4 kilometers) round trip when completed as an out-and-back hike.
The trail begins near Arizona Snowbowl at approximately 9,340 feet (2,847 meters) and climbs more than 3,000 vertical feet before reaching the summit ridge.
Most of the route initially passes through forest before reaching exposed alpine terrain. The final portion is rocky, windswept, and susceptible to rapidly changing weather.
Weatherford Trail
The Weatherford Trail provides another route into the high country and eventually connects with trails near the main summit ridge. It offers a longer approach than the standard Humphreys Trail and passes through varied mountain environments.
Inner Basin Trail
The Inner Basin Trail provides access to one of the most visually distinctive parts of the old volcano. The basin sits within the breached interior of San Francisco Mountain and is especially famous for its stands of aspen.
Access conditions can change seasonally, so visitors should verify current Forest Service road and trail information before traveling.
Kachina, Abineau, and Bear Jaw Trails
Other trails explore the forested slopes of the massif without requiring a climb to Arizona’s highest summit. These include the Kachina, Abineau, and Bear Jaw trails.
They can provide excellent alternatives for hikers interested in forests, fall color, wildlife, and mountain scenery rather than an exposed summit climb.
⚠️ Alpine Restrictions and Trail Protection
Because the upper San Francisco Peaks contain extremely fragile alpine habitat, hikers should pay close attention to current Forest Service regulations.
A Forest Service order currently in effect through December 17, 2029 restricts entry and camping within designated portions of the San Francisco Peaks alpine tundra and Inner Basin. The order includes exemptions for people remaining on designated National Forest System trails and for certain travel across snow-covered terrain.
Regulations can change, so hikers should check the current Coconino National Forest order before visiting the alpine zone rather than relying solely on older trail descriptions.
The purpose of these restrictions includes protecting sensitive alpine vegetation that can take many years to recover from trampling.
🏔️ Field Guide Tip
If you plan to hike Humphreys Peak, start early and carry proper layers even on a warm summer day. Northern Arizona’s summer monsoon season typically brings its greatest thunderstorm risk from July into September, and lightning above tree line is a serious hazard.
Turn around if thunderstorms begin developing rather than trying to race weather to the summit. Carry the Ten Essentials for Hiking, know how to interpret a topographic map, and remember that a high-elevation hike can become considerably more serious than a lowland trail.
Winter travel is a different undertaking altogether. Snow, ice, extreme wind, avalanche terrain, and navigation problems can turn portions of the Peaks into mountaineering objectives. Understanding the difference between hiking and mountaineering is especially important during snowy conditions.
🌤️ Best Time to Visit
The best season depends heavily on what you want to do.
Summer provides the most accessible conditions for ordinary hiking once high-elevation snow has melted. However, July through September is also Arizona’s summer monsoon season, when thunderstorms and lightning can develop quickly.
Early autumn is one of the most scenic periods on the mountain. Aspen groves can turn brilliant shades of yellow and gold, although peak fall color varies from year to year.
Late autumn and spring can bring highly variable conditions. Snowfields, ice, muddy trails, and cold temperatures may persist at high elevations even when conditions around Flagstaff appear mild.
Winter transforms the mountain into a snowy alpine environment. Arizona Snowbowl operates on the western side of the Peaks, while backcountry areas may require winter travel skills and careful avalanche evaluation.
Because conditions change quickly with elevation, visitors should always check current forecasts, road status, trail conditions, and Forest Service alerts.
🧭 The San Francisco Volcanic Field
The San Francisco Peaks are only one part of an extraordinary volcanic landscape.
The surrounding San Francisco Volcanic Field contains more than 600 volcanic features produced during approximately six million years of volcanic activity. Volcanism generally migrated eastward across the region over geological time.
Cinder cones and lava flows are scattered across the country surrounding Flagstaff. One of the youngest and best-known volcanic areas is Sunset Crater, northeast of the San Francisco Peaks, where eruptions occurred roughly 1,000 years ago.
This makes the region a particularly useful place to study how volcanic landscapes evolve. Within a relatively compact area, visitors can see ancient, heavily eroded mountains as well as much younger volcanic cones and lava flows.
💡 Interesting Facts About the San Francisco Peaks
- Humphreys Peak is the highest point in Arizona, reaching approximately 12,637 feet (3,851.9 meters) according to current National Geodetic Survey data.
- The familiar 12,633-foot elevation found in many references comes from older vertical-datum measurements.
- The Peaks are not several unrelated volcanoes. They are primarily the eroded remnants of one enormous stratovolcano.
- San Francisco Mountain may once have stood approximately 15,000–16,000 feet high.
- The mountains contain Arizona’s only true alpine tundra environment.
- The threatened San Francisco Peaks ragwort occurs naturally nowhere else.
- The broader San Francisco Volcanic Field contains more than 600 volcanic features.
- Several Indigenous peoples maintain important spiritual and cultural relationships with the mountains.
- The Peaks can be seen from great distances across the open Colorado Plateau.
- The mountain’s enormous prominence helps explain why it appears so dramatically above the surrounding landscape.
❓ Frequently Asked Questions
What is the highest mountain in the San Francisco Peaks?
Humphreys Peak is the highest summit. Current National Geodetic Survey data give it an elevation of about 12,637 feet (3,851.9 meters), making it the highest point in Arizona.
Are the San Francisco Peaks a mountain range?
They are often described as a small mountain range or group of peaks, but geologically they are more accurately understood as the surviving summit complex of a single large, deeply eroded stratovolcano called San Francisco Mountain.
Are the San Francisco Peaks volcanic?
Yes. The Peaks are volcanic in origin and are part of the much larger San Francisco Volcanic Field.
Is the volcano still active?
The most recent known eruptions associated with San Francisco Mountain itself ended approximately 93,000 years ago. Younger volcanic eruptions have occurred elsewhere within the San Francisco Volcanic Field. It is therefore important to distinguish the ancient stratovolcano forming the Peaks from the broader volcanic field.
Can you hike to the top of Humphreys Peak?
Yes. Humphreys Trail is the standard hiking route to the summit. The trail is strenuous and reaches exposed alpine terrain where altitude, lightning, high winds, snow, and rapidly changing weather can create hazardous conditions.
Can visitors hike anywhere above tree line?
No. Sensitive alpine habitat is protected by special Forest Service regulations. A current order restricts certain entry and camping in designated alpine and Inner Basin areas while providing exemptions for travel on designated Forest System trails and certain snow-covered travel. Always check the latest regulations before leaving established trails.
Why are the San Francisco Peaks sacred?
Numerous Indigenous nations of the Southwest have longstanding cultural, ceremonial, and spiritual relationships with the mountains. The specific meanings, names, traditions, and responsibilities connected with the Peaks differ among communities.
When is the best time to hike Humphreys Peak?
For most hikers, summer through early fall generally offers the most practical snow-free conditions. Summer hikers must pay particular attention to monsoon thunderstorms and lightning. Snow and winter conditions can occur well outside the warmest months at high elevations.
How far are the San Francisco Peaks from Flagstaff?
The massif rises immediately north of Flagstaff, and major recreation areas on its slopes can generally be reached with a relatively short drive from the city. Exact travel distance depends on the chosen trailhead or destination.
🔗 Related Articles
Continue exploring northern Arizona and high-elevation landscapes with these Mountain Field Guide articles:
- Humphreys Peak – Arizona’s Highest Mountain
- Agassiz Peak
- Fremont Peak
- Aubineau Peak
- Doyle Peak
- The Ten Essentials for Hiking
- How to Read and Use Topographic Maps
- Mountaineering vs. Hiking: Key Differences
📚 Sources
- U.S. Geological Survey — San Francisco Volcanic Field and Geology and History of the San Francisco Volcanic Field — volcanic-field size and history, number of volcanic features, age and development of San Francisco Mountain, erosion, and volcanic geology.
- National Geodetic Survey — FRISCO Benchmark, PID FQ0624 — current Humphreys Peak coordinates and NAVD 88 elevation of 12,637 feet, along with the superseded 12,633-foot NGVD 29 value.
- Peakbagger — San Francisco Peaks and Humphreys Peak — summit elevations, topographic prominence, key col, and isolation data.
- U.S. Forest Service — Kachina Peaks Wilderness, Humphreys Trail No. 151, San Francisco Peaks Alpine Tundra and Inner Basin Order, and Names of the San Francisco Peaks — trail information, wilderness management, weather and safety guidance, current alpine restrictions, cultural names, and naming history.
- U.S. Fish & Wildlife Service — San Francisco Peaks Ragwort — endemic alpine plant distribution, habitat, conservation status, and Arizona’s alpine zone.
