The hook
The old highway was left in place when the freeway bypassed it — 31 miles of two-lane road threading through the largest remaining old-growth redwood forest on Earth.
01Why it's worth it
Muir Woods is a garden; this is the forest. Humboldt Redwoods State Park protects Rockefeller Forest, the biggest contiguous stand of old-growth redwood left anywhere — 10,000 acres where the trees run 300 feet and the understory is knee-deep sorrel — and the Avenue is the decommissioned stretch of old US-101 that wanders through it at 35 mph while the freeway hums elsewhere. The scale change is physical: light dims, sound dies, your car becomes a toy. Founders Grove's fallen Dyerville Giant (taller than the Statue of Liberty when it stood; the crash in 1991 registered on seismographs) teaches redwood size better horizontal than any standing tree does vertical. This is past the three-hour line and unapologetic about it — the far-north anchor the way Mendocino anchors the coast, and the reason the radius says "eventually six hours."
02How to experience it
Take the marked Avenue exit off 101 south of Fortuna (or north of Garberville) and drive it end to end, stopping at Founders Grove and the Rockefeller Forest loop at minimum — walking is where it actually happens; the drive alone is the checkbox version. The Eel River bars make summer swim stops. Skip the paid drive-through-tree kitsch unless kitsch is the mood — the free forest is the point of the trip.
The honest note
The hour you arrive decides what this is, and a road-tripper put it better than any guidebook: "Pick a trail and go EARLY walking in the dew with just the forest sounds is religious. Once people, kids, dogs and people with boomboxes (wtf) show up it's just another hike." That is the whole review. Be on a trail before nine or accept an ordinary walk.
Driving it is not visiting it. The Avenue is a 31-mile road and the temptation is to treat it as scenery through a windscreen. The groves only work on foot — Founders Grove and Rockefeller Forest are the short ones.
The roadside attractions are a different product. Drive-thru trees, Confusion Hill and the gift shops sit along the same stretch; they are fun or tacky by taste, but they are not the forest.
From the locals
The strongest framing is a Californian arguing about which places deserve national-park status: "California has some State Parks that are National Park worthy — Humboldt Redwoods (the Avenue of the Giants), all the Big Sur state parks, Anza-Borrego."
And from a family who drove the whole northern route, the detail that places it: "right along this path in Northern California… near the Avenue of the Giants 254. We did this trip over summer, and it was just magical. Stopped and swam at Eel River on the way up and down."