O’Leary Peak
O’Leary Peak is an 8,943-foot (2,726-meter) volcanic summit north of Flagstaff, Arizona, in Coconino National Forest. Rising prominently above the landscape near Sunset Crater Volcano National Monument, the mountain offers sweeping views across the San Francisco Volcanic Field and toward the towering San Francisco Peaks.
Although O’Leary Peak is considerably lower than Humphreys Peak and the other major summits west of it, its substantial prominence makes it an impressive mountain in its own right. A long service road climbs toward a historic fire lookout on the eastern summit, making O’Leary a popular hiking destination for anyone interested in volcanic landscapes and expansive northern Arizona views.
⚡ Fast Facts
| Feature | Details |
|---|---|
| Country | United States |
| State | Arizona |
| County | Coconino County |
| Region | San Francisco Volcanic Field |
| Elevation | 8,943 ft / 2,726 m |
| Prominence | 1,787 ft / 545 m |
| Isolation | 5.22 mi / 8.4 km |
| Nearest Higher Neighbor (NHN) | Sugarloaf Peak |
| Mountain Type | Volcanic dome complex |
| Land Management | Coconino National Forest |
| Coordinates | 35.4022° N, 111.53245° W |
LiDAR measurements place the summit of O’Leary Peak at approximately 8,943 feet, with about 1,787 feet of topographic prominence. Its nearest higher neighbor is Sugarloaf Peak, approximately five miles to the west-southwest.
🌋 A Volcano in the San Francisco Volcanic Field
O’Leary Peak is part of the immense San Francisco Volcanic Field of northern Arizona, a region containing hundreds of volcanic vents spread across the Colorado Plateau.
The mountain is composed largely of rhyodacitic volcanic rocks. Geological studies describe O’Leary Peak as a complex of rhyodacite domes, flows, and smaller pyroclastic deposits, with the principal dome dating to roughly 230,000 years ago. An older andesite flow underlies portions of the rhyodacitic rocks.
That makes O’Leary considerably older than nearby Sunset Crater, whose eruption occurred only about 1,000 years ago.
The result is a landscape where volcanic features spanning hundreds of thousands of years can be viewed within a remarkably small area.
🏔️ A Surprisingly Prominent Arizona Mountain
O’Leary Peak does not rank among Arizona’s very highest mountains by elevation, but its 1,787 feet of prominence makes it much more topographically significant than many higher summits.
The mountain rises conspicuously above the surrounding volcanic terrain and is included among Arizona peaks with more than 1,000 feet of prominence.
This prominence is immediately apparent from Sunset Crater and the surrounding roads. O’Leary forms a broad, forested mountain mass rather than the sharply defined cone associated with younger volcanoes nearby.
Its nearest higher terrain lies toward Sugarloaf Peak and the enormous San Francisco Mountain complex beyond.
🌋 O’Leary Peak and Sunset Crater
One of the most interesting aspects of O’Leary Peak is its proximity to Sunset Crater Volcano National Monument.
Sunset Crater is a dramatically younger volcanic feature formed during eruptions around the late 11th century. Those eruptions created the dark Bonito Lava Flow immediately south of O’Leary Peak.
From portions of the O’Leary Peak route, hikers can look directly across the cinder-covered terrain toward Sunset Crater and its surrounding lava flows.
The U.S. Geological Survey specifically notes that a fire road leading toward O’Leary’s summit can be seen from the Bonito Lava Flow.
Few hikes around Flagstaff provide such a good elevated perspective on the extraordinary concentration of volcanic features northeast of the city.
🔥 O’Leary Lookout
One of O’Leary Peak’s most recognizable features is the O’Leary Lookout, a fire tower standing on the mountain’s eastern summit.
Importantly, the lookout does not occupy the true high point.
The western summit reaches approximately 8,943 feet, while the lookout summit reaches about 8,919 feet. The two high points are separated by only a short distance, but hikers seeking the actual summit need to distinguish between them.
The current lookout tower was constructed in 1959. Forest Service historical documentation describes it as a 30-foot steel tower topped by a 14-foot-square cab.
Its elevated position provides an excellent vantage point for observing the forests and volcanic terrain surrounding Flagstaff.
🥾 Hiking O’Leary Peak
O’Leary Peak offers one of northern Arizona’s better high-elevation training hikes.
The most common route begins near the O’Leary Group Campground and follows a gated Forest Service road toward the lookout. The route is straightforward from a navigation standpoint, but it is long and steadily uphill.
A typical round-trip hike is approximately 9.5 to 10 miles, with roughly 2,000 feet of elevation gain, depending on the exact starting point.
The first portion is relatively gentle before the road begins climbing more aggressively through a series of long switchbacks.
The route passes through ponderosa pine forest while gradually opening increasingly broad views of the volcanic country below.
Eventually, the road reaches a saddle between the O’Leary Peak complex and nearby Darton Dome before continuing toward the lookout.
⛰️ Reaching the True Summit
Hikers should be aware that following the road all the way to O’Leary Lookout does not quite reach the mountain’s highest point.
The true summit lies on the western portion of the mountain and rises roughly two dozen feet higher than the lookout summit.
Peakbagger’s LiDAR data gives the western summit an elevation of 8,943 feet, compared with approximately 8,919 feet for the lookout summit.
Peakbaggers interested in reaching the actual high point therefore need to continue beyond the normal lookout destination.
For many recreational hikers, however, the lookout itself is the natural destination because the road provides easy navigation and the summit area offers excellent views.
🌄 Views From O’Leary Peak
The panorama from O’Leary Peak is exceptional.
To the west and southwest rise the San Francisco Peaks, including Humphreys Peak, Agassiz Peak, Doyle Peak, Rees Peak, and Sugarloaf Peak.
Farther south, Elden Mountain rises above Flagstaff.
The eastern and southeastern views reveal an entirely different landscape dominated by volcanic cones, cinder fields, lava flows, and the unmistakable profile of Sunset Crater.
On especially clear days, the horizon extends far across the Colorado Plateau.
🌲 Forests and Wildlife
O’Leary Peak rises through classic northern Arizona ponderosa pine forest.
The volcanic soils surrounding the mountain support ponderosas along with scattered aspens, junipers, and other high-country vegetation. The landscape becomes more open in places where lava, cinders, fire history, and elevation restrict tree growth.
Wildlife in the broader Coconino National Forest can include mule deer, elk, coyotes, squirrels, numerous songbirds, raptors, and other animals adapted to the forests and open volcanic terrain of the Colorado Plateau.
The transition from forested mountain slopes to stark lava fields around Sunset Crater is one of the most visually striking aspects of the area.
☀️ Best Time to Hike O’Leary Peak
Late spring through fall generally provides the easiest hiking conditions.
Summer temperatures are much more comfortable here than in Arizona’s low deserts, but afternoon thunderstorms are an important concern during the monsoon season. Hikers should consider starting early and avoiding exposed summit areas when storms are developing.
Autumn can be particularly beautiful, bringing cool temperatures and patches of changing aspen.
Winter and early spring can bring substantial snow and ice to the mountain. The road may still be hikable under appropriate conditions, but the outing becomes a winter backcountry trip rather than a straightforward dry-weather hike.
🌎 The San Francisco Volcanic Field
O’Leary Peak is only one piece of an extraordinary volcanic landscape covering much of northern Arizona.
The San Francisco Volcanic Field contains hundreds of vents representing millions of years of volcanic activity. These include cinder cones, lava domes, lava flows, and the huge composite volcano whose eroded remnants now form the San Francisco Peaks.
Nearby mountains illustrate the diversity of this landscape. Elden Mountain is another prominent volcanic dome near Flagstaff, while Sitgreaves Mountain rises west of the San Francisco Peaks.
O’Leary Peak is particularly valuable because its summit provides such an excellent overview of the volcanic field.
📸 What Makes O’Leary Peak Special?
O’Leary Peak combines several qualities that make it stand out among the mountains of northern Arizona.
It has enough prominence to dominate its immediate surroundings, a long but uncomplicated hiking route, an active lookout site, fascinating volcanic geology, and one of the best elevated views of Sunset Crater and the surrounding volcanic field.
Its position also places hikers between two very different generations of Arizona volcanoes: the ancient high mass of the San Francisco Peaks to the west and the much younger Sunset Crater landscape immediately to the south.
For hikers interested in geology, peakbagging, fire lookouts, or simply a demanding day hike near Flagstaff, O’Leary Peak is one of the most rewarding lesser-known summits in the region.
🔗 Related Articles
- Sugarloaf Peak
- San Francisco Peaks
- Humphreys Peak
- Agassiz Peak
- Doyle Peak
- Rees Peak
- Elden Mountain
- Sitgreaves Mountain
📚 Sources
- Peakbagger — O’Leary Peak
- Peakbagger — O’Leary Peak Lookout
- Arizona Highways — O’Leary Peak Trail
- U.S. Geological Survey — Sunset Crater and Bonito Lava Flow
- U.S. Geological Survey — Volcanic Geology of the O’Leary Peak Area
- USDA Forest Service — Lookouts in the Southwestern Region
- Recreation.gov — O’Leary Group Site, Coconino National Forest
