Tom's Thumb, McDowell Sonoran Preserve: Tom's Thumb Trailhead, Phoenix - Scottsdale - Mesa, Arizona
Tom's Thumb - 4.3 miles
McDowell Sonoran Preserve: Tom's Thumb Trailhead
|Round-Trip Length:||4.3 miles|
|Start-End Elevation:||2,805' - 3,830' (3,830' max elevation)|
|Elevation Change:||+1,025' net elevation gain (+1,420' total roundtrip elevation gain)|
Tom's Thumb - 4.3 Miles Round-Trip
Tom’s Thumb is a granite spire that caps a high ridge on the northeast side of McDowell Sonoran Preserve. This iconic formation is visible from miles around, and has quickly become one of the area's most popular hiking and climbing destinations.
About 1.4 million years ago, rising magma intruded overlying rhyolite and quartzite rock layers and lithified into granite.
Crystals formed and produced a course-grain rock in pockets where magma cooled slowly; faster cooling magma holds fewer crystals and a finer grain. Both are high-traction surfaces prized by climbers and mountain bikers.
Exposed granite has been dramatically rounded by erosion, with horizontal and vertical joint patterns in larger rock masses. This rounded, light colored rock contrasts sharply with the dark, jagged basalt and rhyolite found throughout the McDowell range.
Visitors may notice a strong resemblance to Joshua Tree National Park, whose predominate monzogranite rock is of similar origin and complexion.
The Tom’s Thumb Trail leads 2.15 miles through magnificent rock gardens to the eponymous feature. High ridges offer sweeping views over the Preserve and Verde River Valley, and trail connections for The Lookout, East End and Windgate Pass:
Tom’s Thumb Trail heads south through large plots of well-spaced brush, a good place to find jackrabbit, roadrunner, quail and a variety of songbirds. Sculpted boulders litter the bajada, which is noticeably absent of saguaro and barrel cactus.
The trail rises gently past the Feldspar Trail to a climbing access spur (.45 miles : 2,980’), past which it steepens considerably on tightly wound switchbacks.
Despite challenging grades the surface is smooth from finely eroded granite (grus), a welcome departure from many local trails.
The trail climbs 683’ in just .9 miles to a crest overlooking the McDowell interior, and a surreal landscape of immense rock features and lush vegetation (1.35 miles : 3,663’).
It dips to the East End Trail split (1.6 miles : 3,582’), and curls west up to the Tom’s Thumb access trail (1.9 miles : 3,721’). You’ll pass the Glass Dome en route, a worthwhile destination in itself.
The spur breaks north and weaves nimbly through large outcrops to the base of Tom’s Thumb (2.15 miles : 3,830’). This spacious, elevated area is easy to explore, with many shaded nooks and terrific views in every direction.
Interactive GPS Topo MapKey GPS Coordinates - DATUM WGS84
- N33 41.636 W111 48.132 — 0.0 miles : Tom's Thumb Trailhead
- N33 41.332 W111 48.344 — .45 miles : Climbing access trail split
- N33 41.097 W111 48.280 — .92 miles : Climbing access trail split
- N33 40.862 W111 48.225 — 1.35 miles : Reach crest, dip to East End Trail
- N33 40.751 W111 48.241 — 1.55 miles : Tom's Thumb - East End Trail split
- N33 40.774 W111 48.531 — 1.9 miles : Tom's Thumb Trail spur - bear right
- N33 40.899 W111 48.665 — 2.15 miles : Tom's Thumb (base of thumb)
- Higher elevations with the opportunity to find shade amid large boulders make this trail a good choice in warmer months.
- Tom's Thumb Trailhead sees heavy use, especially on weekends. Arrive early to secure parking and avoid crowds.
Rules and Regulations
- Dogs must be on a hand held leash at all times.
Directions to Trailhead
Tom's Thumb Trailhead is located on the northeast side of McDowell Sonoran Preserve.
This newly renovated and expanded trailhead is located 11.9 miles from HWY 101 on McDowell Mountain Ranch Road.
From Highway 101, take the Pima Road Exit (#36) and head 4.7 miles east on Pima to Happy Valley Road. Turn right on Happy Valley for 4.5 miles to McDowell Mountain Ranch Road. Follow signs (right) for Tom's Thumb Trailhead.
McDowell Sonoran Conservancy 16435 N Scottsdale Rd. Suite 110 Scottsdale AZ, 85254 480.998.7971