OCTOGENARIAN Edith Hepplethwaite, a Senior Olympics gold medalist, has bicycled it three times a week for a decade to volunteer at the Kennedy Center, the Library of Congress and the National Gallery of Art. Justice Department lawyer Jerry MacLaughlin pedals it daily to work and says he beats the Metro, "except when I have to slow for geese." Rick Kaplan rides it for recreation, a bit at a time. "I like to look at planes, get a vista, get off and go into Old Town, get back on, and see birds and estuaries," he says.

They're talking about the Mount Vernon Trail, the granddaddy of our region's bike trails, an 18.5-mile stretch skirting the Potomac from Teddy Roosevelt Island to George Washington's Mount Vernon. On clear days, it offers spectacular views of Washington across the Potomac as it swoops and curves along the Virginia shore. New elevated bridges, virtual bicycle superhighways, carry traffic safely over dangerous intersections at National Airport. Boardwalks and bridges cross wetlands and marshes. Attracting about a million users annually, it's one of the region's, and the nation's, most popular recreational trails.

Thank two unsung Alexandria volunteers for the Mount Vernon Trail. Thirty years ago, they petitioned the Park Service, cut a deal and organized volunteers who shoveled tons of gravel one winter to lay its first, 4.5-mile section. When it jammed with users soon after opening, their trail proved the popularity of urban recreational trails, sparking development of our still-expanding network of more than 150 miles of trails and making an impact nationally, as well.

In 1971, there was no Mount Vernon Trail, no Crescent Trail arcing through the District, no wooded Rock Creek network or 45-mile W & OD rails-to-trails pathway. That spring, Alexandria housewives Ellen Pickering and Barbara Lynch talked often over their grocery carts about an idea: Why not build a bike trail along the George Washington Memorial Parkway? Their families could bike it on weekends, and Barbara's husband could commute to work in the District.

Those days, a "bike boom" was on. Adults wanted distance rides for their new 10-speed bikes. Mothers sought safe places for their kids to ride as suburbs increasingly paved the region. Earth Day inspired two-wheel commuters, and regional bicyclists numbered 100,000.

Bicycle activists rallied on Bike Day, May 15, 1971, pedaling heavy, steel 10-speeds and upright Schwinns down Rock Creek Parkway, closed for the occasion. Standing in the rain on that Sunday in slickers and wet sneakers at the Lincoln Memorial, they cheered speakers who called for Washington to become "a model city for bicyclists."

But they had little to celebrate, despite half a dozen years of activity.

Pickering and Lynch were not given to idle talk. They took their families to a June "Bike In" on the closed, northbound lanes of the George Washington Memorial Parkway; and at Columbia Island, where bikers lolled about resting on the grass, they fanned out and went to work, pulling out petitions to build a Mount Vernon bike trail. They collected signatures. Hundreds of them.

They sent 700 signatures to Jack Fish, an assistant director at the National Park Service, whose office had closed Rock Creek Parkway for Bike Day. He knew about the Bike Day speeches. The bike boom was forcing trails on his rights of way, like a dangerous track near the George Washington Memorial Parkway. He arranged a November meeting. "He didn't know us from beans," Pickering recalls.

When the volunteers met him, they found little opposition -- but less money. "It's always budget," says Fish; in a region stretching west to Harper's Ferry and packed with national treasures like the Washington Monument, he had none to spare. Nor did he have a precedent for a recreational bike trail like the one these volunteers were seeking.

He decided to go out on a limb, though. If the Park Service, he proposed, would provide right of way, crews to blade the base and gravel by the ton, could the volunteers muster the labor to build a trail? If so, he figured, he could find $9,000 in another budget.

The volunteers agreed to the deal on the spot.

The first Saturday, when Parkway workers arrived with five shovel, Pickering and Lynch brought 40 volunteers. That day they sent for more shovels, then another dump truck of gravel, and spread it all before noon.

Every Saturday, from November through February, they turned out the volunteers, garbed in gloves and wool to fight the cold. Pickering brought the cocoa and marshmallows. Lynch counted gravel piles park crews left during the week and dialed for Saturday workers, and she squeezed shovels in her squareback along with her four kids. Families, Scouts, students and bicyclists worked hard and moved fast to stay warm. Hard candies cut the dust in their throats. Drivers honked and waved -- and even pulled over to help.

The volunteers stalled only once, a sub-zero February day. Driving rain had cased the gravel piles in thick ice. Everyone milled about in the shadow of the 14th Street bridge, raising their voices over the traffic above. Then someone grabbed a shovel, and smashed a hole in the ice. Another enlarged it. Soon everyone was at work.

April 15, 1972, hundreds gathered south of Alexandria at Belle Haven Park, where officials cut the ribbon on 4.5 miles of new gravel bike trail. They had connected the park with the 14th Street bridge, by way of city streets in Alexandria. In all, Pickering, Lynch and their 400 recruits shoveled 4,240 tons of gravel and contributed 5,350 hours of labor.

"Some people pooh-poohed the trail at first," Pickering says. But by summer, use was heavy and constant, the weekends, jammed. Parkway Superintendent Dave Richie secured $135,000 by special appropriation to extend the trail to Mount Vernon. The Park Service did the work, completed in 1973, with advice from the volunteers. Richie widened lanes, engineered curves, built bridges and sent scenic excursions through wetlands like those at Dyke Marsh (built with assistance from the Army Corps of Engineers). Even today, engineers from other cities travel here to review those blueprints.

Pickering and Lynch, now white-haired grandmothers, still ride the Mount Vernon Trail. They are quick to tell you how many people helped build the first, gravel section. But they provided the spark. Of their role, Pickering simply says, "We were just women who said, 'Why don't we?' " And adds, with a smile, "And, we did!"

THREE OTHER TRAILS ROCK CREEK TRAIL -- 25 miles, from the Lincoln Memorial to Lake Needwood in Montgomery County.

CAPITAL CRESCENT TRAIL -- 12 miles, starts in Georgetown and ends in Silver Spring.

W & OD TRAIL -- 45 miles of rails-to-trails path from Arlington to Purcellville, Va., accessible in Falls Church, Vienna, Reston, Herndon and Leesburg.

CLUB RIDING POTOMAC PEDALERS TOURING CLUB -- Organizes about 1,000 local and regional tours a year. www.bikepptc.org. 202/363-8687.

WASHINGTON AREA BICYCLIST ASSOCIATION -- Publishes a good book on local rides, "Greater Washington Area Bicycle Atlas: 67 Scenic Tours in the Mid Atlantic Region." Online, click their "Maps & Publications" at www.waba.org. 202/628-2500. Now a popular destination for two-wheelers, the Mount Vernon Trail was just a bright idea by two Alexandria housewives 30 years ago.