The Warm Springs ski run on Bald Mountain in Sun Valley, Idaho, is considered by many to be the best stretch of downhill in the country. The two-mile-long, top-to-bottom screamer charges straight through a natural gully with banked sidewalls before opening up to the width of a California freeway. It never wavers from the fall line and maintains an average pitch of 35 degrees, without a single blind turn to slow you down. Three hundred sunny days a year, ridiculously generous snow making, and smart grooming mean Warm Springs is also always in top condition. "Warm Springs has this cultlike following," says Zach Crist, X Games gold medalist and lifetime Sun Valley local. "Some skiers are so addicted to the speed and thrill, they ski it every day all winter long."

But what makes Warm Springs really special is that while clocking your fastest time on skis ever, you may pass by only a dozen people during the entire run. Baldy, as it's known to locals, sees so few skiers on a daily basis that fresh corduroy is often found well into the afternoon. It's not just Warm Springs that's empty – it's the tree skiing in Cold Springs and the ridgelines on the South Slopes; it's the lift lines and the parking lots. "Sometimes I stand at the top of Baldy shaking my head and laughing," says Crist. "There's no one else around – just me, a few friends, and this incredible mountain all to ourselves. It has terrain as good as anywhere, with only a fifth of the people."

Sun Valley is a true anomaly in the landscape of modern ski resorts – likely the result of having once been the most accessible ski town in the country, then later becoming one of the least accessible. Founded in 1936 by Averell Harriman, chairman of Union Pacific Railroad, Sun Valley was meant to be America's first destination ski resort, our answer to European hot spots like St. Moritz. Harriman chose Sun Valley for its beauty and high desert climate, but also for its proximity to Ketchum, a stop on his railway line. At a time when commercial air travel had yet to take off, he put the resort on the map by offering a straight shot from Hollywood, luring the stars and starlets of the era with free stays, Austrian ski instructors, and giant hot pools at the base of the mountain. 'Life' magazine featured a skier riding Sun Valley's new chairlift on a 1937 cover.

Eventually, though, Harriman turned to politics, sold everything, and discontinued rail service to Ketchum. By the sixties, just as other ski resorts across the U.S. began cashing in on the boom Sun Valley had created, America's most famous one became its most isolated. Sun Valley was almost certainly headed for bankruptcy until Sinclair Oil owner Earl Holding decided to buy himself a hobby. In 1977 Sinclair began spending millions on high-speed lifts, new day lodges, and the largest and most advanced snow-making system in the world. And he didn't sell a single acre of land to offset the costs. Skier numbers no longer seemed to matter – the resort's busiest season on record was three decades ago – and money was poured into making a great mountain instead of marketing campaigns.

Sun Valley is tricky to get to – surrounded by three different mountain ranges, including the largest roadless area in the lower 48 – but also beautifully trapped in time. The only way in is via its tiny and famously unreliable airport or a three-hour drive from Boise. Bald Mountain is on public land, and strict ordinances have kept its hillsides and ridgelines free of development. The resort is built around a real town full of regular people who run hardware stores and pharmacies. There are remnants of its heritage as a getaway for the rich and famous – Bruce Willis, Arnold Schwarzenegger, and Tom Hanks own homes here – but the real celebrities in Sun Valley are guys like Jeff Mintz, a local window washer with a bushy, often frost-covered mustache who skies every single day between Thanksgiving and closing day. Or Bozo Cardozo, a heli-skiing guide and woodworker known for his hand-built folding guitars. "It all comes down to authenticity," says local Langely McNeal, a nationally ranked ski-cross racer. "Sun Valley feels like a ski town built around skiing, not a real estate development with a ski resort built on to add value."

Sun Valley isn't for those looking for a quick weekend ski trip. Don't expect a cookie-cutter village at the base of the lifts or ski-in, ski-out accommodations. In fact, don't expect many hotels at all. Most people who visit Sun Valley in winter rent a privately owned condo or house, ideally right at the base of Warm Springs. On the mountain itself, everyone seems to know one another – and you could end up doing laps in Mayday Bowl with the same 30 people all day. Afterward, skiers with aching quads swing by Chateau Drug, the place to grab some Advil – or a hammer or a birthday card. Apple's Bar and Grill is a museum of Sun Valley skiing, with Crist's X Games gold medal on display in one corner and Picabo Street's World Cup helmet in another. The Pioneer Saloon is a museum of the West, with a 10-foot-long antique hunting gun hanging over the bar, deer heads mounted over booths, and fading photos of Hemingway on the walls.

Earl Holding passed away last April, and his heirs seem ready to finally share Sun Valley with the rest of America. The airport has picked up just enough direct flights from a few major cities to keep the number of tourists at a healthy minimum, and music festivals like Sol Fest and Reggae in the Mountains are bringing in an entirely new generation. A new terrain park, halfpipe, and ski-cross course have given Baldy a wider variety of terrain and brought high-profile contests. Sun Valley feels poised for a transformation. For some, that means getting there as soon as possible to experience one of America's last great independent ski resorts just the way it is; for others, it's an exciting investment in Sun Valley's future. "I love seeing people's reactions when they visit Sun Valley for the first time," says McNeal. "It's like they've been let in on some great secret. More people are coming, and the whole place is buzzing – just leave the big-city attitude at home."

The Perfect Day: Speed runs down Warm Springs never get old, and you could spend all day on it. But if it's a Saturday, be sure you make it back to the top of Baldy by the end of the day to join the 3:30 Club. Locals meet every week at Lookout lodge and party until long after the resort closes, before skiing down the deserted mountain in the fading light. Back in town, get a true Idaho wilderness experience at Frenchman's hot springs on Warm Springs Road, and then a sense of Sun Valley history with an après beer at the 90-year-old Casino.