The Humboldt Redwoods Marathon, Half Marathon & 5K are located in the beautiful HUMBOLDT REDWOODS STATE PARK, about 200 miles north of San Francisco and 40 miles south of Eureka. The marathon & half marathon start together (at 9am) at the Dyerville Bridge which is on the famous Avenue of the Giants near the majestic Founders Grove in Humboldt Redwoods State Park.