Quicksilver Endurance Runs

The Quicksilver Endurance Runs start and finish at the Hacienda entrance of Almaden Quicksilver County Park, in the hills at the southern edge of San Jose. The Quicksilver Running Club held its first race in 1983, a 50-miler from Calero Park to Quicksilver County Park with four finishers, and 2026 was the 42nd edition. Today there are two races on hilly singletrack and fire road: a 100K of 62 miles with more than 13,000 feet of climbing that heads into the Sierra Azul Open Space, and a 50K of 30.3 miles with more than 6,000.

The 100K starts at 4:30 a.m. with a 17-hour limit and the 50K at 7:00. The 2027 races are on May 8. Every official 100K finish inside 17 hours is a Western States 100 qualifier, and the 100K is part of the USATF Pacific Mountain-Ultra-Trail Grand Prix.

Both races start and finish at the Hacienda entrance of Almaden Quicksilver County Park on Almaden Road. The 100K, by the race's summary 62 miles with more than 13,000 feet of climbing, leaves the park for the Sierra Azul Open Space by way of Mt. El Sombroso and the climb past Priest Rock, with out-and-back sections where bib numbers are recorded at the turnarounds. It has eight aid stations and the 50K five, some visited twice. The 50K is 30.3 miles with more than 6,000 feet of climbing. Hiking poles are not allowed in either race, runners may have one pacer at a time, and the race is cupless. The club says the courses have been the same since 2024.

Entry is first-come on UltraSignup, with a waitlist once a distance fills. 2027 registration opens on November 14, 2026; the race's own site says midnight Pacific and UltraSignup says 6:00 a.m. The 2027 fee and field cap are not published yet. Runners can roll over 50 percent of the fee before February 8, 2027, with no refund or credit after.