San Jose's Alum Rock Park is a steep canyon in the Diablo Range foothills on the city's east side, and it's an easy drive from downtown. KQED has called it "one of the less-visited jewels in the Bay Area's crown."
A former spa
The city says the park was founded in 1872 and calls it one of California's oldest municipal parks. Wikipedia calls it the oldest. From 1890 to 1932, it was a nationally known health spa with 27 mineral springs, an indoor swimming pool, a tea garden, a restaurant and a dance pavilion. Visitors rode the Alum Rock steam railroad from downtown for a quarter, according to the city. Rail service into the park ended on July 11, 1932. In the 1970s, the city removed most of the buildings and refocused the park on nature. Some of the stonework and old railroad supports are still there.
The name comes from a mix-up. The powder coating some of the rocks near the entrance was mistaken for alum. KQED says it's actually sulfur, gypsum and other substances, a hint of the area's volcanic past. The springs bubble up warm and smell of sulfur. Wikipedia notes that the magnitude 5.6 Alum Rock earthquake on Oct. 30, 2007, 19 years ago today, caused a dried-up spring to start flowing again.
Trails and wildlife
The 720-acre park has about 13 miles of trails, including six miles of horse trails and three miles of bike trails. Hikers can use all of them. Routes range from the mostly level Penitencia Creek Trail to switchbacks up the South Rim and North Rim trails, which have views over the Santa Clara Valley. Some trails are part of the Bay Area Ridge Trail and connect to Open Space Authority land. Look for black-tailed deer, quail, red-tailed hawks and turkey vultures. Bobcats are around but hard to spot.
Current closures
According to the city, the Penitencia Creek Trail is closed at the Trestle Bridge section, and visitors should use the park road to pass under the bridge. The Mineral Springs Trail is closed because of erosion, but you can still see the historic grottos from the Penitencia Creek Trail. Metered lights on Penitencia Creek Road control traffic while the city repairs damage from the 2023 atmospheric river storms.
Know before you go
- Hours: 8 a.m. to half an hour after sunset.
- Address: 15350 Penitencia Creek Road, San Jose.
- No dogs: The city treats the park as a protected wildlife sanctuary and doesn't allow dogs.
- Youth Science Institute: This nature center, founded in the park in 1953, has live animals, including non-releasable hawks and owls. The city lists its museum hours as Wednesday through Friday, noon to 4 p.m., and weekends, 10 a.m. to 4 p.m.
- Rules: No balloons, amplified sound, or drums. Beer and wine are allowed in picnic areas only. Fires and barbecues may be restricted during fire season.