Mount Baldy Wilderness Preserve

Mount Baldy Wilderness Preserve is located off Mt. Baldy Road within a few miles of the historic mountain summit, along the border of Los Angeles and San Bernardino counties in the Angeles and San Bernardino National Forests. The preserve was acquired by Watershed Conservation Authority in 2014 to protect significant natural and scenic resources and critical wildlife and landscape connections to adjacent public lands owned and managed by the USFS. The preserve protects part of a 20-mile reach of San Antonio Creek, whose natural streambed reflects an unmodified flood regime. The preserve is flanked on the East and West by the Cucamonga and Sheep Mountain designated Wildernesses, both of which are habitat for big horn sheep.



Mount Baldy Wilderness Preserve is the location of trailheads for popular trails. (Read trail reviews here). 


Invasive Species Management

In 2021, WCA received a grant through the River and Mountains Conservancy’s Wildfire Prevention Grant Program for removal of invasive species at the Preserve. Invasive Spanish broom (Spartium junceum) is a rapidly growing species which increases fuel loads, displaces habitat for native wildlife, and interferes with public safety and enjoyment of this preserve. This species was present before WCA acquired the land, and had spread over the intervening years. Inland Empire Resource Conservation District prepared an Invasive Species Management Plan for the preserve. A multi-year effort to remove this invasive species by California Botanic Garden and San Gabriel Valley Conservation Corps began in 2022 and will continue through 2025.


Natural history of Mount Baldy Wilderness Preserve


The topography of Mount Baldy Wilderness Preserve is formed by a landslide, which resulted in the landform endearingly named 'Hogsback.' This landform has been the topic of numerous articles and geology field trips.

Geology and Fracture Geometry in Source Region of Hogback Landslide by Reginald Agunwah (2020)

Hog Back: A grossly stable prehistoric translator rock block slide by Lawrence J. Herber (1987)

A Day in the Field with Tom Dibblee A Guidebook by Johnathan Nourse, Thomas Dibblee, and Peter Weigand (2003)

Geology and Hydrology in the Eastern San Gabriel Mountains by Kenney et al (2010)


The unique conditions provided by the geology of the canyon makes it home to a number of reptiles and amphibians.

Herpetofauna guide to the Preserve by William Flaxington (2023)


At any given time of the year, observant visitors are likely to see butterflies in the canyon that would not be seen in the developed areas in the Los Angeles basin. That is because many butterflies found at the Preserve are associated with native plants on site for their life cycle requirements.

This butterfly collection of species found in San Antonio Canyon was created by Bill "Butterfly" Gendron, and is kept at Mount Baldy Lodge


Glendora Naturalist Dick Swinney compiled this list of plants found at the Preserve

In the coming year, California Botanic Garden and San Gabriel Valley Conservation Corps will be adding to our record of plants at the Preserve. If you would like to participate in this project to document plant and animal species on the Preserve, please send a note to staff at indicating your interest.