Big Rock Day Use Area & River Access is a Six Rivers National Forest site on the Trinity River in the town of Willow Creek, in eastern Humboldt County, California. The Lower Trinity Ranger District runs it as a day-use river access, and the Forest Service lists swimming, picnicking, river fishing and non-motorized boating as its uses. It sits on the town side of the river a few blocks from the Willow Creek ranger station, and on hot summer afternoons it is one of the busiest swimming spots on the lower Trinity.

From the junction of Highway 299 and Highway 96 in the middle of Willow Creek, drive about a quarter mile north on Highway 96 and turn right toward the river. Cars park in the lot above the water, and a short walk leads down to the boat ramp and the shoreline. The coordinates the Forest Service publishes (40.94685, -123.63315) point to the parking area, not the shoreline. The Lower Trinity Ranger District office in Willow Creek can be reached at (530) 629-2118.

There is no marked swim area and no lifeguard. People swim and wade from the shore near the ramp, and the site takes its name from a large rock out in the river. Depth changes with the flow, so a spot that was knee deep in August can be over your head in June. The Trinity here is fed by releases from Lewiston Dam far upstream plus its tributaries. Water readings at Willow Creek were near 60 F in late June 2025 and about 70 F by late August 2025, so the river is far kinder in midsummer than in spring. Expect sunbathers, swimmers and rafters sharing the water on warm weekends.

The Forest Service lists no fee for Big Rock, and parking and river access are free. It is day use only, with no camping. Posted hours are not given on the forest's page, so plan on daylight use. The site has shaded picnic tables. The Forest Service description mentions two vault toilets while its amenity table says restrooms are not available, so don't count on a working toilet. There is no drinking water, so bring your own.

The river is the hazard here. On March 31, 2021, three swimmers from Arcata got stranded on a rock in the river at Big Rock and a Humboldt County sheriff's deputy, helped by people on the beach, brought them to shore with rescue gear. The Sheriff's Office warned afterward that spring is too early to swim the Trinity because of high, fast water, and asks swimmers to check river levels and Trinity River release schedules before going in, never swim alone, keep life jackets on young children, and not treat inflatable toys as flotation. Calm-looking water on this river still moves fast enough to pin a swimmer against a rock. If the current feels strong, get out.

Big Rock is also a working fishing and boating access. Anglers fish for half-pounder steelhead below the rock early in the morning, before the swimmers and rafters show up, and rafters and kayakers use it to put in or take out on the lower Trinity. Willow Creek's grocery stores, gas and restaurants are a few minutes away along Highway 299.