Wilderness, as the conservationist Aldo Leopold put it, is "the very stuff America is made of." As pioneers settled our continent, their encounter with wilderness shaped our national character. Today, as Americans flock to our national forests, parks and other federal lands, many seek the wilderness, savoring its scenic splendors and a quiet that's increasingly rare.

Hikers and hunters, birders and anglers, families with kids and those like us, who are closing in on their 80s, find in wilderness the opportunity to reconnect with pioneer skills and relive our national history.

This year we celebrate the 40th anniversary of the 1964 Wilderness Act and what it has accomplished through the decades. Using the authority granted in this historic conservation law, Congress has designated wilderness lands in 44 states, ranging from the huge — a single 13 million-acre wilderness in Alaska — to a 5-acre wilderness island in Florida and the 875,000-acre Olympic National Park wilderness in Washington. Thus far, we have preserved 106 million acres, giving the wilderness character of each area the strongest possible protection: Only Congress can alter an area's enabling legislation.

Protecting wilderness areas is not some top-down federal decision. It is the most "small-d" democratic land allocation process we've invented. Potential wilderness areas are identified by on-the-ground agency staff and local people who know the land best, and then the decision to carry a bill is made by our elected representatives in Congress, led usually, though not always, by the local congressional delegation.

Happily, this has not been a partisan process. The Wilderness Act was first supported by a liberal Democrat, Sen. Hubert Humphrey of Minnesota, and a conservative Republican, Rep. John Saylor of Pennsylvania. Westerners like Sens. Clinton Anderson, D-N.M., Thomas Kuchel, R-Calif., and Frank Church, D-Idaho, were in the forefront. Jimmy Carter signed laws designating more land than any other president, while Ronald Reagan signed the most wilderness bills — 43 laws designating areas in 31 states — including both of ours in Washington and Arkansas.

As senators who worked to protect wilderness areas in our states, we are pleased to be members of Americans for Wilderness, a nonpartisan committee helping to highlight the nation's special wild places in this 40th anniversary year of the Wilderness Act. Presidents Gerald Ford and Jimmy Carter head the list of honorary members. This diverse group of more than 100 is chaired by Barbara Kingsolver, Robert Redford and Christopher Reeve, and includes Maya Lin, Morgan Freeman, Emmylou Harris, Federico Pena, Bill Bryson, Alice Waters and E.O. Wilson.

As Congress acts on new wilderness proposals, the nonpartisan, bottom-up grassroots pattern continues. Take the proposed Wild Skykomish Wilderness in Washington state, now awaiting final action in Congress. Championed by two Democratic senators, this bill has been endorsed by the Bush administration and unanimously passed the Republican Senate last fall. Washington representatives of both parties are now working to finish the job in the U.S. House of Representatives.

Congress is now actively considering bills to designate similar broadly supported new wilderness areas in California, Puerto Rico and New Mexico, with others expected for Virginia, Idaho and Nevada — all with local congressional support in both "blue" and "red" states.

The American people understand that in Leopold's words, "the rocks and rills and templed hills of this America are something more than economic materials." Consider what those polled told the federal government's National Survey on Recreation and the Environment: Seventy percent favored protecting more wilderness areas in their own states, with only 12 percent opposed. The margin for rural residents was 63 percent favoring more wilderness; 19 percent opposed.

Why do Americans feel so strongly about protecting their wilderness heritage? Why do they rally to preserve not-yet-protected wilderness when drilling or logging threatens, as in New Mexico's Otero Mesa, Montana's Rocky Mountain Front, or the unspoiled remnants of Arctic Alaska? The federal government's polling shows that Americans value wilderness not only for recreational pursuits but also for scenic beauty, watershed protection, habitat for wildlife and more.

Above all, we think — and the polling confirms — that a key factor in why Americans so overwhelmingly favor protecting more wilderness is its legacy value. That is, the deeply felt, widely shared sense of obligation to our children, grandchildren and all future generations to leave these areas just as they are so that others will also know wilderness in their time.

Dale Bumpers and Dan Evans are contributors to Writers on the Range, a service of High Country News (hcn.org). Dale Bumpers of Washington, D.C., is a former Democratic governor and U.S. senator from Arkansas; Daniel J. Evans of Seattle is a former Republican governor and U.S. senator from Washington state.