The Opal Creek Valley contains 50 waterfalls, five lakes, and 36 miles of hiking trails. It forms the largest intact stand of Old growth forest in the western Cascades and 500-1000 year old trees are common. The most abundant trees are Douglas-fir, Western Redcedar, and Western Hemlock. Common hardwoods include big leaf maple and red alder. Understory vegetation includes huckleberry, vine maple and rhododendron. There are eight trails in Opal Creek, totaling 36 miles. These are remnants of the early day prospecting and fire access routes.
The wilderness was designated September 30, 1996 after a nearly twenty year battle to protect the area from logging and mining. In 1980, the District Ranger of the Detroit Ranger District, Dave Alexander, vowed to "cut Opal Creek." By late 1981, clearcut boundary markers were placed. Lawsuits were filed, scenic rivers were designated, and multiple bills to protect the area failed, including an attempt to make it a state park. When books and photo essays were published in the early 1990s, national attention was brought to the area. Finally, in 1996, after working with all stakeholders, including environmental groups, local communities and representatives of the timber industry, to draft consensus legislation, United States Senator Mark Hatfield obtained passage of expansive legislation to protect Opal Creek. With the input of a federal advisory committee, the area has been managed and preserved by the U.S. Forest Service pursuant to the Opal Creek legislation.
Preserving the old growth mixed Douglas fir and hemlock forest that comprises the Opal Creek Wilderness area was crucial for protecting populations of the Northern Spotted Owl, Strix occidentalis caurina, which has very specific habitat requirements. At up to 18 inches tall and a wingspan of up to 4 feet, this is one of the largest owls in North America; it is fiercely territorial and rarely migrates. In spite of their size, populations of spotted owl are still threatened by habitat loss, competition with expanding barred owl populations, and low reproductive rates.