Alum Rock Park in East San Jose is a hidden jewel, set in a canyon at the foot of the Diablo Range.  

If San Jose is known for its dry vegetation, how did it get this 720-acre park in a lush green forest? 

The answer is Penitencia Creek, which flows here and gives the park much of its charm. Alum Rock is California’s oldest municipal park, dating from 1872. 

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At the turn of the 20th century, Alum Rock Park had 27 mineral springs, an indoor swimming pool, tea gardens and a restaurant. Visitors arrived by a steam-driven railroad. Today, all of that is long gone. But you can still walk to the stone grottos that housed the springs and see remnants of the bridges from the train line.  

Visiting Alum Rock is like visiting an outdoor museum. There are signs and plaques and old stone pilings that tell this history.  

The park is celebrating its 150th anniversary this year, with events scheduled through October, including many guided walks. 

This 1913 grotto is one of many that used to offer visitors access to one of Alum Rock Park’s 27 mineral springs. (Alison Sokoloff/Bay City News)

While there’s plenty of history in Alum Rock Park, there’s also plenty of nature. Listen to the blue jays, or look for red-tailed hawks and turkey vultures that soar above. The Youth Science Institute has a small nature center here, although it’s never been open when I’ve visited, so its aviary and displays remain a mystery.   

The park is a popular destination, drawing thousands of visitors a year. During the week, though, it’s very quiet.  

Alum Rock Park has ample parking, and there’s room to roam on both paved and dirt trails. The main trail follows Penitencia Creek past some of the 149 picnic tables and 85 barbecues in the park. There’s also a children’s playground.  

Alum Rock Park offers an impressive view of San Jose. (Alison Sokoloff/Bay City News)

On a recent weekday hike, we followed the South Rim Trail to the top. It was a vigorous workout, up a series of shaded switchbacks, past purple, orange, yellow and white wildflowers. Ferns grew on the sides of the creek. At the top, we had a great view of downtown San Jose. 

The park got its name from the alum salt that was supposedly in its hillsides. It turned out that the rocks didn’t contain alum, but the name stuck both to the park and the surrounding neighborhood in East San Jose.  

My favorite building at Alum Rock Park is the log cabin, located in the middle of the park. It stands in contrast to the adobe historic buildings usually associated with the Santa Clara Valley. According to a historical marker, it was built between 1914 and 1916 out of redwood logs from the Santa Cruz Mountains and is “a memorial to the pioneers.” Today it’s fenced off. 

Alum Rock is a great place to visit any time of the year. In the summer, its picnic areas are shaded. In winter and fall, it’s a great place to hike in search of sunshine on its high ridges. In springtime, everything is in bloom.  

Alum Rock Park is three miles from Interstate 680. From I-680 North, take the McKee Road exit. From I-680 south, take the Berryessa Road exit. There is a $6 parking fee for some of the lots in the park. No dogs are allowed.  

For more information on events planned for the park’s 150th anniversary, the city has a website:

For information on the Youth Science Institute, call (408) 258-4322 or go to