High Noon is when a proper western should start, but we're still waiting for Floyd Landis, Lance Armstrong, and George W. Bush. The 2007 Great Divide Race kicks off in 18 minutes here on June 15 at the First and Last Chance Bar, in Roosville, Montana, and the border crossing is buzzing with the carnival vibe of a gumball rally: 24 mountain bikers in clean, bright kits, tinkering with gear straps and barrel adjusters as they wait to begin the 2,490-mile self-supported race from the Canadian border to Antelope Wells, New Mexico, on the Mexican line.

Everyone's nerves are showing. MYSTERY RACER is listed on the Website roster, and various forums are speculating wildly about which celebrity will show. Mike Curiak, 39, is the GDR's official race director and the course record holder—16 days, 57 minutes, in 2004. Curiak's rivals, now the 2007 favorites, are trading greetings: Anchorage bike wrench Pete Basinger, 27, who holds the Iditasport record, and North Carolina maître d' Matthew Lee, 37, the winner of the last two GDRs—best time, 17 days, 22 hours, 30 minutes, in 2006. The wild card, balding and goateed Jackson Hole drywall contractor and Iditasport runner-up Jay Petervary, 34, is fiddling with his XM satellite receiver, which is wired to a mini solar recharger and preset to perpetual reggae and NPR: "I'm gonna get the weather."

The rest of the field consists of two dozen underemployed dreamers who may have gotten ourselves in over our heads. I haven't felt anything like this since the day I got married; I haven't eaten since last night, but Matt McFee, a thirty-something computer geek and mountain-bike guide from Durango, is putting down his second or third hot dog as if he might not see another before the Fourth of July. Rick Hunter, a lanky California frame builder, tries to relax, surfer cool, on a picnic table next to his custom rigid ride, a cyclocross/cross-country hybrid with a couple of extra bottle cages for when this stunt hits the desert. Three middle-aged British endurance riders are keenly filling their camera's memory card. And long-haired San Diego bike messenger Noah Dimit, 23, has waved goodbye to his grandparents and is heating soup on his backpacker's stove: Jesus on a Stumpjumper.

It's no small feat to get your rig to this border—like marriage, the GDR is a tough race to start and a tougher one to quit. Ask Nathan Bay. Bay is a 37-year-old baker, elk hunter, and recovering alcoholic from Bozeman sporting Ted Nugent camo on a green GT single-speed. Bay will tell you that mountain biking helped save his life—but be careful, because fat-tire rehab is a slippery slope, and you could find yourself in Roosville pointed south.

The mystery rider decides not to show; either that or he isn't very mysterious. As for me, undertrained and overloaded, it's too late to turn back. My name is down on a legal pad next to the model of my bike, as if it were a racehorse: Jon Billman riding Santa Cruz Blur. Matthew Lee on Cannondale Caffeine. Matt McFee on Surly Karate Monkey.

There's no starting gun, no eulogy, no ready-set-anything. "OK, beat it," Curiak says at the electronic beep of noon, and we're off. A half-dozen riders—Lee, Petervary, Basinger, and three more—mash their 29-inch wheels to the front. Eight miles in, they are out of sight; with 2,482 miles to go, the rest of the pack has become a very loose chase group.

"Viva New Mexico!" a man in shorts and woolly socks yells from the sidewalk, jumping up and down like a Tour de France lunatic. "Go! New Mexico! Yeah!" His are the last cheers we'll hear for the rest of the race—the GDR has no spectators, other than those who follow the daily updates we'll leave on a Colorado answering machine to be posted online.

I'm already in over both spindles and Mexico is still an oil change away.