Alum Rock Park

From 1890 to 1932, the park served as a spa, with 27 mineral baths, a natatorium (an indoor swimming pool), a tea garden, restaurant, a dance pavilion, a hotel and a zoo.  Alum Rock Park was accessible by railroad from downtown San Jose.  The trains are long gone, and overuse led to the extinction of many of the mineral springs.  However, the remains of the rail lines and baths are still found throughout the park. 

Alum Rock Park provides the residents of northern California’s largest city with 720 acres of natural, rugged beauty and outdoor activities such as hiking, horseback riding, bicycling, and picnicking. 

Originally known as “the reservation”, the park got its name at the beginning of the 20th century from visitors mistaking thenardite rocks at the park entrance for alum. 

Early promoters of the railroad claimed a two-story boulder found near the mouth of Penitencia Creek canyon was a meteorite and weighed two thousand tons which would have made it one of the largest anywhere in the world.   These attempts to draw visitors to the park by train were later undermined by research that determined the rock was 389 tons and made of manganese, an earthly element still found in smaller amounts along the banks of the Penintencia Creek.   Its extraterrestrial origins disproven, the city later sold the original rock to a ‘mining man’.  A smaller rock of the same element is on display at the visitors center. 

The canyon walls are steep and contain a variety of grasses, poison oak, holly leaf-cherry, sagebrush, and scattered live oak trees.   California bay laurel, madrone, and California buckeye can also be found, and along Penitencia Creek, big leaf maple, white alder, and western sycamore provide shade for the ferns.  Rattlesnakes, black-tailed deer, brush rabbits, quail, red tailed hawks and turkey vultures are common.