Diablo Trails Challenge Half Marathon, 10K, 5K & 50K

Saturday, April 8, 2023 • Walnut Creek, CA • Course Map

Said to be the point of creation, Mount Diablo looms over northern California 3,864 feet over the ground — splitting the skies of the San Francisco Bay area. According to Miwok and Ohlone mythology, Mount Diablo and Reed’s Peak were once islands and that the creator, Coyote, and his trusty assistant, Eagle-man, made the world and the Indian people from these two mountains.

Besides the chance to muse over the bizarre folklore, there are two great reasons to be involved in this race. First, a portion of the entry fees will go to Save Mount Diablo — an organization devoted to the preservation of the park’s priceless peaks, foothills, and watersheds.

The second reason to register is that this race is everything for everyone — from the person who thinks wearing “Shape Ups” is a good workout to the gold medalist in the London Olympic 10,000 meter race.

Runners can choose between running the 5K, 10K, half marathon or 50K — each group starting and finishing the race at Castle Rock Park in Walnut Creek. If you want to walk or hike the course, you’re welcome to come out and participate without anyone rushing you to the finish line. The 50K race, however, does have a course time limit of 10 hours.

If you’re up for the 50K, you can look forward to combing through Round Valley, Morgan Territory, Mount Diablo State Park, and Shell Ridge Open Space.

Race Weather & Climate

Located among the hills overlooking San Francisco Bay in Northern California, about 25 miles northeast of downtown San Francisco, Walnut Creek typically sees mild to sometimes warm weather in April, a month that has brought record temperatures as low as 29 degrees (in 1999) and as high as 98 degrees (in 1996).

On race day (April 8), the average low is 43ºF and the average high is 73ºF.

Past Results

Course Map

See the race route map for the Diablo Trails Challenge Half Marathon here.

Starting Time

  • 6:30 AM – 50K
  • 8:30 AM – half marathon
  • 9:00 AM – 10K
  • 9:30 AM – 5K


  • $85 and up – half marathon
  • $125 and up – 50K
  • $67 and up – 10K
  • $58 and up – 5K


To reserve your spot in the 2023 running of Walnut Creek’s Diablo Trails Challenge Half Marathon, 10K, 5K or 50K trail race, register online at RaceRoster.com here.

Official Race Website



Ever run in the Diablo Trails Challenge? Share your impressions here, or post your review in the Comments below.

See more races in: April, California

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