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


Thunder Mountain


Location: Los Angeles County, about 12 miles north of Cucamonga, 48 miles from Los Angeles


Auto ClubLos Angeles and Vicinity
Forest ServiceAngeles National Forest
USGS ToposTelegraph Peak 7½, Mount San Antonio 7½
Official HPS Maps TPO file - Save to your computer then open with National Geographic TOPO!
 Viewable JPG file - Approximately 1.3 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)

Nearby Peaks: Telegraph Peak, Timber Mountain

Printable version of this route


(USFS Adventure Pass may be required)
Distance: 11 miles round trip on road and trail
Gain: 2400 '
Time: 4-5 hours round trip
Rating: Class 1, moderate

Original: Warren E. von Pertz, July 1969


  • Take the 210 freeway east to Baseline Road exit in the City of Claremont. Turn left (west) at the bottom of the off-ramp onto Baseline Road.
  • Almost immediately, take the first right (north) onto Padua Ave.
  • Go 1.8 miles north on Padua to the intersection with Mount Baldy Rd. Turn right (northeast).
  • Take this road northeast and then north about seven miles to Mt. Baldy Village.
  • Continue another four miles to the intersection with San Antonio Falls Road on the left (gated). Park here.

Note: There is a good parking lot for ridesharing in this area. To get there, after turning west on Baseline Road, continue past Padua Avenue a short distance to Mills Avenue. Turn north on Mills, and continue to Mt. Baldy Road. The parking lot is at the northeast corner of this intersection.


  • From the parking area (6160'), pass the gate and hike up the road to Baldy Notch at the top of the ski lift.
  • Turn right (southeast) and follow a road up to the summit.


Do not hike up the slope beneath the ski lift. This is not legal.


The ski lift at the end of Baldy Road operates in the summer months on weekends and some holidays. It is possible to take this (for a fee) to Baldy Notch. This significantly reduces the gain and distance. A popular trip is to take the lift to the notch, then climb Thunder Mountain, Telegraph Peak, and Timber Mountain, returning via Icehouse Canyon to the site of the old Ice House Resort. This requires a car shuttle.

History of Summit Signature

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

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