Henry Cowell Redwoods State Park sprawls across 4,650 acres of mixed redwood and Douglas fir forest in the Santa Cruz Mountains, with the San Lorenzo River running through a deep canyon carved into sandstone. The signature feature is the old-growth coast redwood grove—towering trees that predate the Gold Rush, some over 1,500 years old—accessible via a paved loop that winds through the understory where the air stays cool and damp year-round. Visitors walk among massive trunks and ferns, with the river audible but often hidden by vegetation. The terrain ranges from river-level flats to steeper hillsides, and parking areas sit near both the main redwood groves and less-crowded picnic zones. The trail system includes over 15 miles of routes ranging from easy riverside walks to steep climbs up to Henry Creek and the ridge overlooking the canyon. Winter brings the heaviest rainfall and fastest river flow but fewer crowds; summer and early fall offer the most stable weather, though heat can intensify in the canyon.

Dogs are allowed on leash in the campground and on paved roads, including the main paved loop through the redwood grove itself. However, dogs cannot access any of the park’s dirt trails, which make up the bulk of the system. This means no Redwood Trail, no ridge hikes, no water crossings on the forest floor. Your dog sees the park from pavement: the loop through the grove, the campground, and paved pull-offs. That loop is substantial and pleasant, but if you came hoping for forest hiking, the restriction eliminates the majority of available routes. Visitor access runs dawn to dusk, with standard state park entrance fees. Parking fills quickly on weekends, especially in summer. The campground operates year-round with first-come availability or reservations through the standard state parks system.

If genuine trail mileage with your dog is the goal, Henry Cowell’s restrictions may disappoint. Armstrong Redwoods State Natural Reserve in Guerneville, about 90 minutes north, allows dogs on all trails including redwood groves, making it a stronger choice for dog hiking in old-growth forest. At Henry Cowell itself, maximize the paved loop—take it twice if you like, stop at picnic areas, and use the campground as a base if staying overnight. The river can be accessed from the campground area where dogs on leash can reach the water on dirt stretches near the paved zone. The San Lorenzo River supports steelhead and coho salmon, and the park sits within a protected remnant of the once-vast coastal redwood range.