Hike by Rob Lehman, originally published in the July 2010 issue of Bay Nature magazine
California's oldest municipal park (founded in 1872) occupies 720 acres and has 13 miles of excellent hiking trails within Alum Rock Canyon in the Diablo Range foothills, just minutes east of downtown San Jose. The park was once a world-renowned spa and resort; tourists traveled from afar by electric train to soak in naturally heated mineral baths. Entrepreneurial developers built rock grottoes, a hotel, a pavilion, and a bathhouse. By 1894 Alum Rock Park had added an aviary, a restaurant, a carousel, an arcade, and even a zoo. And it was very popular: On one notable Sunday, 10,000 people visited the park.
Today most of the man-made attractions are gone, but a few are still standing, along with beautiful WPA-era stone bridges built in the 1930s. The canyon supports diverse habitats, with south-facing slopes of grasses, sagebrush, poison oak, and coast live oak, and north-facing slopes that feature live oak, madrone, bay laurel, and buckeye. Alder, sycamore, and bigleaf maple thrive along Penitencia Creek, providing shade for lush ferns.
But where's the alum rock? A local farmer mistook a whitish mineral called thenardite along the creek banks for the more valuable alum, and his name for the canyon stuck.
Getting there Take Interstate 680, and exit at McKee. Go east on McKee (right), and left on White Road. Take White to Penitencia Creek Road. Follow Penitencia Creek Road into the park. Parking is $6.