Hundred Peaks Emblem
Sierra Club Hundred Peaks Section Sierra Club


About Us



Peak List




Register Box

Climbing Guides




Find us on Facebook

Join the Sierra

** Use at Your Own Risk **

See the Retired Peak Guides in the Archives for Microsoft Word and other versions of this peak guide.


Iron Mountain #1


Location: Los Angeles County, about 13 miles north of Claremont, 42 miles from Los Angeles


Auto ClubLos Angeles and Vicinity
Forest ServiceAngeles National Forest
USGS ToposMount San Antonio 7½, Mt Baldy 7½, Glendora 7½
Official HPS Maps TPO file - Save to your computer then open with National Geographic TOPO!
 Viewable PDF file - Approximately 2.4 megs
 GPX file or Google Earth KML file to download to GPS units and other map software (How to use GPX and KML files)
 Routes as shown on CalTopo using the above files (How to use CalTopo)

Printable version of this route


(USFS Adventure Pass may be required)
Distance: 14 miles round trip on trail and cross-country
Gain: 7200' total, 6600' out plus 600' on return
Time: 10-12 hours round trip
Rating: Class 1, very strenuous
Navigation: Moderate

Original: Howland Bailey, April 1969


  • From the intersection of I-210 and Azusa Avenue (SR 39), drive north on Azusa Avenue about 12 miles to the intersection at the East Fork Bridge.
  • Turn right and drive 6.1 miles to a parking lot at the end of the road. Park here.


  • From the parking area, pass the locked gate and hike north and east up the road about 1/2 mile to the beginning of trail 8W16 on the right at Heaton Flats. There may be a sign "Heaton Flat Trail".
  • Take this trail, keeping right at an immediate fork. Follow the trail up to the top of the ridge. Continue on the trail over several small bumps to its end at Allison Saddle (4582').
  • Leave the trail and head north up the ridge following an obvious use trail up to the summit.


On the return trip the ridge forks about 1/4 mile below the summit. Be sure to the follow the use trail off to the left at this point. Many experienced hikers have made a mistake at this point.

Wilderness permits are required to hike the Heaton Flat Trail. They are available at the following locations:

  1. Self-serve at a kiosk near the entrance to the parking lot.
  2. The USFS Entrance Station on SR 39.
  3. The San Gabriel River Ranger District Office at 110 N. Wabash in Glendora.
  4. By mail from:
    San Gabriel River Ranger District
    Angeles National Forest
    110 N. Wabash
    Glendora, CA 91741
    (626) 335-1251


This peak has been climbed from many different directions including a route that traverses Mount San Antonio. All of these routes are very difficult and should not be attempted by inexperienced hikers.


This peak is considered to be the hardest climb in the San Gabriels. Also known as Big Iron, it was originally called Sheep Mountain by the early miners in San Gabriel Canyon because of the large bands of Bighorn sheep that formerly roamed the slopes. The Geological Survey, which mapped the San Gabriels in the 1890's, ignored the local designation and gave it its present name.

History of Summit Signature

Climbing Archives

Please report any corrections or changes to the Mountain Records Chair.

Sierra Club

Angeles Chapter

Desert Peaks

Lower Peaks

Sierra Peaks

San Diego Peaks

© Copyright 2015-2023 - All Rights Reserved Hundred Peaks Section, Angeles Chapter, Sierra Club
Most recent update: Tuesday, 15-May-2018 21:18:04 PDT
Valid HTML 4.01!