Owing to Idaho libertarianism and overlapping jurisdictions, jumping here is what it rarely is on such man-made objects elsewhere: legal. While it's legal to jump off many cliffs and natural objects (excluding those in national parks), the owners or overseers of bridges, towers, and buildings are reluctant, for obvious liability reasons, to grant jumpers permission. The constant threat of prosecution means that most BASE jumping happens covertly, often under the cover of night. As word has spread that there's a beautiful bridge you can leap from in the light of day, BASE enthusiasts from all over the world have arrived in force. More than 100 of them showed up for a jumpfest this past Labor Day weekend. And the town has opened its arms to jumpers, even featuring them on the hats and T-shirts sold in the visitor center near the bridge.

Miles began his jumping odyssey in 1992 while a student at California's Chico State University. His friend Jim Fritsch, founder of a local bungee outfitter, hired Miles for his ground crew. Miles began doing jumps, and from the start his experience with gymnastics and diving showed in his acrobatic flair. After graduating in 1993, Miles made the short hop up to Squaw Valley, California, in the Lake Tahoe area, and stayed 11 years. He ski-bummed, worked bungee, and took odd jobs to support a jump habit that grew to include skydiving after he received certification in 1995. He soon fell in with a group of jump-happy friends at the nearby Parachute Center, in Lodi, California, a crew that included Shane and Frank "the Gambler" Gambalie, Miles's roommate at the time and the man responsible for getting the rest of them into BASE jumping.

A leader of the sport's late-nineties new wave, Gambalie eventually agreed to mentor Miles and Shane, teaching them skills like BASE-specific parachute packing, the ability to judge wind direction, speed, and object height, and how to approach different types of landing zones. Sadly, in 1999, after a successful but illegal jump off El Capitan, Gambalie drowned in the Merced River while being chased by Yosemite park rangers.

Such tragedies dot the history of BASE jumping. Unlike skydivers, whose reserve parachutes and high-

altitude jumps allow them to fix certain problems, if something goes wrong during a BASE jump, it tends to go irreparably wrong. In the past 25 years there have been nearly 100 BASE fatalities—at least six in 2005 alone—the vast majority from impact with the BASE object itself. (Miles broke his shoulder skydiving but has avoided any BASE-related mishaps.)

In spite of its obvious dangers, BASE is in the midst of a growth spurt, emerging, like other "extreme" sports before it, from the outlaw shadows into the pale light of mild exposure. "We've had a huge growth wave in the last five years," says Tom Aiello, 33, head of the Snake River BASE Academy, in Twin Falls. Growth, however, is relative. Statistics are a tricky thing in a sport that is still mostly underground; current estimates put the number of BASE jumpers worldwide at about 5,000, though the number who jump regularly is probably a quarter of that.

But none of this deters Miles. "I'm all about proving that BASE is a total spectator sport," he says, explaining the larger purpose of his record attempt. He dreams of BASE being in the X Games and wants to convince a wider audience to see jumpers as athletes rather than as lunatics.

His publicity-hungry attitude has attracted criticism from some in the BASE community, who see Miles as a glory hound whose antics could endanger the sport's legality in places like Twin Falls. But he's determined to take BASE off the fringes, partly out of necessity. Although Miles has several paying sponsorships (including Red Bull, Patagonia, Smith, and Teva), has started a jump school in Twin Falls, and is hopeful that a TV pilot about his record attempt will be picked up for a cable series ("a reality show built around jumping off stuff"), BASE jumping isn't paying all the bills yet.

"If this idea works," he says, flashing a grin, "this is a catalyst for hugeness."