South Mountain: Thondum Wihom Trail

Formerly known as "Geronimo Trail"

2026-11-11 kingsnake Hiking 0

Notice the lack of flowers on Thondum Wihom Trail, approaching Buena Vista Lookout.
Notice the lack of flowers on Thondum Wihom Trail, approaching Buena Vista Lookout.

Thondum Wihom Trail is located on the north side of Phoenix South Mountain Park / Preserve, where Dobbins Rd. curves north to become 20th St., in a more upscale area of south Phoenix. The east side of that Dobbins Rd. / 20th St. curve is designated the Thondum Wihom Trailhead, but there is no lot. No side-by-side parking. Parallel only. And there’s not much room.

Thondum Wihom Trail: Some of the neighborhoods are even gated, and the rest have no parking signs, so rather than risk it, I walked ⅔ mile over on Euclid Ave., from Mormon Trailhead on 24th St. It's an easy leg warmup.
Some of the neighborhoods are even gated, and the rest have no parking signs, so rather than risk it, I walked ⅔ mile over on Euclid Ave., from Mormon Trailhead on 24th St. It’s an easy leg warmup.

Thondum Wihom Trail was known as Geronimo Trail until November, 2023. “Thondum Wihom” is an Akimel O’oodham term meaning “bright thunder”. The O’oodham reservation is located west and south of South Mountain — the area I skirted on my Loop 202 survey hikes.

Thondum Wihom Trail signs are green. Every sign I saw, the "Thondum Wihom" was spray-painted over. I wonder if an angry Apache did it?
Thondum Wihom Trail signs are green. Every TW sign I saw, the “Thondum Wihom” was spray-painted over. I wonder if an angry Apache did it?

I’m not sure where the original 1930 trailhead was, but Thondum Wihom Trail remains 2.5 miles long, climbing ~1,200 feet. 96 years later, Thondum Wihom Trail still passes by the Boy Scout camp. (How does the BSA keep all it’s Arizona camps open when membership has dropped 70% since 2001?) From 20th St., the trail squeezes between two fencelines, and some “no trespassing” houses.

After passing by the Boy Scout camp, Thondum Wihom Trail begins climbing. The first climb is 400 ft. in a half mile, a healthy 15% slope.
After passing by the Boy Scout camp, Thondum Wihom Trail begins climbing. The first climb is 400 ft. in a half mile, a healthy 15% slope.

Thondum Wihom Trail then drops 80 ft. to a wash crossing. I searched for petroglyphs a couple hundred yards up & down wash, but found nothing but 🐝s. From multiple experiences with wild bees in Arizona: No need to panic. Don’t wave your arms, or try to slap them. Those are the scouts. Simply back away, give them a wide berth, and after a hundred feet or so of leeway, they will back off. 👍

Not many desert flowers on Thondum Wihom Trail, despite temps in the high 70s and massive rain a few weeks ago: Just a few scattered creosote and brittlebush. So, here's some edible wolfberry fruit.
Not many desert flowers on Thondum Wihom Trail, despite temps in the high 70s and massive rain a few weeks ago: Just a few scattered creosote and brittlebush. So, here’s some edible wolfberry fruit.

As Thondum Wihom Trail begins climbing out of the wash, there is an unmarked trail to the right. That is a ⅔ mile downhill bail to the scout camp. The second climb is 580 ft. in a mile, which sounds like a lot, but it was a noticeably more moderate 11% slope. At the top of the climb, there’s a use trail back, and to the right, ¼ mile to an informal, less obstructed, observation point.

Halfway up Thondum Wihom Trail's second climb, looking north down 16th St., towards downtown Phoenix (left) and Piestewa Peak (right).
Halfway up Thondum Wihom Trail’s second climb, looking north down 16th St., towards downtown Phoenix (left) and Piestewa Peak (right).

From the top of Thondum Wihom Trail’s second climb, it is only 300 yds. to the bench at Buena Vista Lookout, and another 100 yds. past the bench to the small parking lot on Buena Vista Rd. at Maricopa Trail / National Trail. Unlike nearby Dobbins Lookout, no U.S. Army Signal Corps stone fort.

Many folks will make a 7.0 mile, 1400 ft. AEG loop of Thondum Wihom Trail, Buena Vista Lookout, National Trail, and Mormon Trail. Instead, I headed straight down. Back at the scout camp, I took Beth Dr. and 22nd St. to Mormon Trailhead, which saves a whopping ¼ mile over Euclid Ave. and 20th St.

Unlike National Trail, Thondum Wihom Trail has no mountain bikes. In fact, I only saw one other hiker on it. (She actually risked parking on 20th St.) Tons of people on Mormon Trail though.
Unlike National Trail, Thondum Wihom Trail has no mountain bikes. In fact, I only saw one other hiker on it. (She actually risked parking on 20th St.) Tons of people on Mormon Trail though.

Mormon Trailhead Directions: From I-10 in south Phoenix, take exit 151B, south onto 32nd St. Stay right. In 0.3 miles, turn right on Broadway Rd. In 1.0 miles, turn left on 24th St. (There is no 24th St. exit from I-10.) Follow 24th St. 2.8 miles south to its end at Mormon Trailhead.

Park Map: South_Mountain_Park_Trail_Map (pdf)

GPS File: Thondum_Wihom_Trail_South_Mountain

Distance: 7.03 mi.

AEG: 1,328 ft.

Time: 3h 02m

Rumble Video

Vimeo Video

Hiking Thondum Wihom Trail, Phoenix South Mountain from Preston McMurry on Vimeo.