Glaciers shaped the Hoh River valley thousands of years ago, grinding through rock to create the broad, low-gradient floodplain where the rainforest now thrives. The Hoh people, the valley's original inhabitants, knew this landscape long before any European cartographer drew it on a map. Within Olympic National Park, the forest is protected from commercial logging, though between the park boundary and the Pacific Ocean, much of the surrounding forest has been cut within the last century. Pockets of old growth remain outside the park, but the protected core is where the ecosystem reaches its fullest expression. In 2024, approximately 460,000 people visited the Hoh District, making it one of the most popular destinations in a park that draws millions.

The dominant trees are Sitka spruce and western hemlock, but the forest's character comes from what grows on them. Epiphytes colonize every available surface: mosses, ferns, and lichens like lettuce lichen, which requires the cool, moist conditions found only under old-growth canopy and serves as food for deer and elk. The Hall of Mosses Trail, a short 0.8-mile loop near the visitor center, offers the most concentrated view of this phenomenon, where bigleaf maples wear thick coats of spikemoss that transform them into green sculptures. The Spruce Nature Trail extends 1.2 miles with interpretive signs identifying the trees and plants. Coast Douglas fir, western red cedar, red alder, vine maple, and black cottonwood round out the canopy, each occupying its niche in a layered system that extends from the forest floor to the treetops.

Roosevelt elk graze the meadows and riverbanks, their herds sometimes numbering in the dozens. The northern spotted owl hunts from the old-growth canopy above. Black bears, cougars, bobcats, and coyotes move through the understory. On the forest floor, the banana slug works its slow essential labor, breaking down organic matter into the nutrients that feed the next generation of growth. But even the banana slug faces competition: the black slug, an invasive species from Northern Europe, has been encroaching on its territory. Meanwhile, naturalists have been working to reintroduce fishers, small carnivorous mammals nearly extirpated from Washington state. The Pacific tree frog fills the air with its distinctive chorus, a sound so ubiquitous it serves as the forest's ambient soundtrack.

In December 2024, flooding on the Hoh River washed out portions of Upper Hoh Road, the only vehicular access to the rainforest and its visitor center. A bomb cyclone the previous month had weakened the embankment between road and river. Previous storm damage had been repaired with emergency federal funding, but disruptions to federal services in early 2025 left the timeline uncertain. Washington Governor Bob Ferguson announced in March 2025 that the state would fund most of the estimated $650,000 in repairs, supplemented by contributions from more than 100 private donors. The road was fully repaired by May 5 and reopened to traffic on May 8, restoring access to one of the Pacific Northwest's most visited natural wonders. The episode underscored both the forest's vulnerability to climate-driven flooding and the depth of public attachment to this place.