You’re standing on a sidewalk, and a guy next to you just... leaves. He doesn't walk away; he steps over a chest-high railing and vanishes into the abyss of the Snake River Canyon.
Most people visiting the I.B. Perrine Bridge for the first time have that "wait, is that allowed?" moment. Honestly, if you did that anywhere else in the U.S., you’d probably end up in the back of a squad car. But here in Twin Falls, Idaho, it's just another Tuesday.
The Perrine Bridge isn't just a way to get from Jerome to Twin Falls on U.S. Route 93. It's a 1,500-foot-long anomaly in American law and engineering. It's the only man-made structure in the United States where BASE jumping is legal 365 days a year without a permit. No paperwork, no "Bridge Day" waiting lists—just you, a parachute, and 486 feet of Idaho air.
The Bridge That Almost Wasn't
People think the current steel arch has always been there, but that’s not even close to the truth. Back in 1927, they opened the original "Twin Falls-Jerome Bridge." It was a spindly cantilever thing that looked like it belonged in a black-and-white silent film. Back then, it was the third-highest bridge in the world.
Think about that for a second. In 1927, in the middle of the Idaho desert, they built something that rivaled structures in Europe and major metro areas. It cost 60 cents to cross back then. A fortune for a farmer in the 20s.
The current I.B. Perrine Bridge we see today—the one that looks like a giant, rusty-brown rainbow—replaced the old one in 1976. It cost about $10.5 million. If you’re a math person, you know that in today’s money, that’s a massive steal for a structure that carries thousands of heavy trucks daily. They actually built the new bridge right next to the old one. For a brief window in 1976, you could see both side-by-side, like a "before and after" photo in real life.
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Who was I.B. Perrine anyway?
Most folks assume Ira Burton Perrine was some famous architect. He wasn't. He was a rancher and a dreamer. He’s basically the guy who looked at the dry, dusty "Magic Valley" and said, "I bet I can fix this with water." He pioneered the irrigation systems that turned this high desert into some of the most productive farmland in the country. Without him, Twin Falls is probably just a gas station and a tumbleweed.
Why 486 Feet is the Magic Number
When you look down from the pedestrian walkway, the Snake River looks like a tiny green ribbon. It’s a long way down. Specifically, 486 feet.
In the world of BASE jumping (Building, Antenna, Span, Earth), that height is "kinda low" but "sorta perfect." It’s high enough that you have time to deploy a parachute and steer, but low enough that the adrenaline hits you before you even realize you’ve stepped off.
- The Drop: You fall for about 3 seconds before you have to pull the pilot chute.
- The Landing: Most jumpers aim for the Mogensen Trail or the grassy areas near the river.
- The Hike: There’s no elevator. If you jump, you’re hiking back up the canyon walls or getting a boat ride.
I’ve seen jumpers from all over the world—Russia, Australia, France—sitting in the grass at the Twin Falls Visitor Center, packing their chutes like they’re folding laundry. There's a weirdly chill community vibe there. It’s not just for the pros, either. You can actually book a tandem BASE jump here. Imagine strapped to a stranger, falling toward a river while tourists take photos of you from the sidewalk. It’s a trip.
What Most Tourists Miss
Most people pull into the Visitor Center, take a selfie with the bridge in the background, and leave. Big mistake.
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If you walk east along the Canyon Rim Trail for about two miles, you’ll hit the site of Evel Knievel's failed 1974 canyon jump. You can still see the massive dirt ramp. He tried to clear the canyon in a steam-powered "Skycycle." He didn't make it (the parachute deployed early), but standing there gives you a sense of just how wide this gap really is.
The bridge itself is a truss arch. The engineering is actually pretty wild because they used a "stayed cantilever" method. They built the arch out from both sides of the canyon simultaneously, holding the pieces up with cables until the two halves met in the middle. If they were off by even a few inches, the whole thing would have been a disaster.
Quick Specs for the Nerds:
The main span is 993 feet. The total length is 1,500 feet. It’s currently the eighth-highest bridge in the U.S. It handles everything from sub-zero Idaho winters to 100-degree summer days without breaking a sweat, thanks to the way the steel arch allows for thermal expansion.
Getting There and Staying Safe
If you're planning a visit, here’s the reality. It’s windy. Always. Even on a "calm" day, the wind whips through the canyon like a freight train. If you’re walking the bridge, hold onto your hat. Literally. I’ve seen dozens of hats floating down toward the Snake River.
Parking is free at the Twin Falls Visitor Center on the south end. There are great trails on both the north (Jerome) and south (Twin Falls) sides.
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Wait, is it safe to walk?
Totally. There are high concrete barriers between the cars and the sidewalk. But the railing on the canyon side? It’s high, but it’s not a cage. If you have vertigo, maybe stay toward the middle.
Actionable Next Steps for Your Visit
Don't just drive over it. To really experience the I.B. Perrine Bridge, you need to see it from three different angles.
- The Top-Down: Walk to the middle of the bridge on the east sidewalk. This is where the BASE jumping platform is. Wait ten minutes; someone will likely jump.
- The Bottom-Up: Drive down to Centennial Waterfront Park. You can rent a kayak and paddle right under the bridge. Looking up at 486 feet of steel from the water level makes you feel incredibly small.
- The Horizon View: Hit the Canyon Rim Trail at sunset. The way the light hits the rusted steel and the basalt canyon walls is why they call this the Magic Valley.
If you’re feeling particularly brave, check out the local tandem BASE operators. They usually require a bit of a safety briefing, but it’s the only place in the country you can do it legally. If not, just grab a coffee at the visitor center and watch the "human birds" fly. It’s cheaper and much easier on the heart rate.
The bridge is open to pedestrians and traffic 24/7, but the best viewing is definitely during daylight hours when the jumpers are active. Check the wind speeds before you go; if it’s over 15 mph, the jumpers usually stay grounded, and the walk across the bridge becomes a bit of a workout against the gusts.