Where does the river go? Wyoming’s Sinks Canyon has stumped scientists for forty years

The canyon that’s been hiding its secret for centuries

Six miles outside Lander, Wyoming, a river walks into a mountain and doesn’t come out the other side. Not right away.

Not where you’d expect. The Middle Fork of the Popo Agie River slides into a limestone cavern, disappears completely, and then shows up again a quarter mile down the canyon in a calm pool full of enormous trout.

Scientists have been studying it since the 1980s and still can’t fully explain it. That alone is worth the drive.

A river with a name as wild as what it does

The park takes its name from the geological event that defines it: a river that sinks.

“Popo Agie” comes from the Crow language and translates roughly to “gurgling river,” which feels right once you stand next to it.

The 600-acre park sits in Wyoming’s Wind River Mountains, managed by the state’s Division of State Parks and Historic Sites.

It’s not a huge park by any measure, but what happens here inside those 600 acres is harder to explain than anything you’d find in a place ten times the size.

Humans have been coming here since the last ice age

People figured out this canyon long before any state agency did.

Archaeological evidence puts human activity here going back thousands of years, all the way to the last ice age.

For centuries, Indigenous peoples and migrating wildlife used the canyon as a natural corridor through the mountains. Wyoming bought large portions of the land in 1939 and 1953 to protect the wildlife and the fishery.

By 1971, the state made it official, designating it as the first park established under Wyoming’s newly formed Recreation Commission.

The underground mystery that still stumps geologists

Here’s what they know. Dye tests conducted since the 1980s confirmed that the water entering the Sinks and the water reappearing at the Rise are the same water.

The trip underground takes over two hours to cover a quarter mile. But here’s where it gets strange: more water flows out at the Rise than goes in at the Sinks.

Geologists think Sawmill Creek in the next canyon drains into the same underground limestone system, adding to the flow. The passages are too narrow for divers or cavers to get inside, so nobody knows the exact route.

Feed trout the size of your forearm for a quarter

The Rise is the pool where the river resurfaces, and it’s full of rainbow and brown trout that have had more than a century to grow without anyone catching them.

Fishing has been banned here since a stone power generator went up nearby in 1919. The fish aren’t stocked; they swim up on their own to spawn.

From an observation deck overlooking the pool, you can buy fish food from a vending machine for 25 cents and watch the trout come right to the surface.

The pool flows year-round, even when ice forms along the edges in winter.

Three rock types and 300 climbing routes in a few miles

Climbers from around the world come to Sinks Canyon specifically for what happens to the rock as you move deeper into it.

Within a few miles, the geology shifts from sandstone to limestone to granite as the canyon approaches the Wind River Range.

That gives climbers over 300 documented routes ranging from 5.6 beginner lines to 5.14 expert pitches. The canyon walls face south, so they catch direct sunlight throughout most of the year.

Lander hosts the International Climbers’ Festival each July, a gathering that’s been running since 1994 and just hit its 33rd year.

Hike to a waterfall with a rock waterslide at the top

The trail most people tackle is the 1.5-mile path to Popo Agie Falls, a series of cascading waterfalls on the Middle Fork of the river.

You start at Bruce’s Parking Area just outside the state park boundary in the Shoshone National Forest.

The trail follows the river through wildflower meadows with granite walls rising on either side, climbing 600 to 800 feet along the way.

At the top, there’s a natural swimming hole and a smooth rock waterslide that locals treat as a rite of passage. Mid-to-late summer is the safer time to try it; early season water runs fast and high.

Four trails that show you completely different canyon worlds

The park has trails built for every pace. The Popo Agie Nature Trail is a one-mile loop starting at a suspension bridge, threading through sagebrush, forest, and aspen groves.

The Canyon Trail stretches four miles into the Shoshone National Forest with views of the canyon walls.

The North Slope Trail runs along the northern wall through Douglas fir forests where bighorn sheep and mule deer move through the trees.

The Sunnyside Trail is a two-mile path open to hikers and non-motorized bikes, though it closes to pets from December through April to protect mule deer wintering in the area.

Wyoming’s first certified dark sky park sits in this canyon

In 2023, Sinks Canyon became Wyoming’s first International Dark Sky Park.

It took years of work: the park replaced its outdoor lighting with shielded fixtures and motion sensors to cut down on light pollution.

The steep canyon walls do some of the work naturally, blocking outside light from bleeding in. After dark, the park runs night sky programs that cover constellation tours and nocturnal wildlife.

If you’re staying at the campground, you can stay out as late as you want. Day visitors need to check posted park hours.

Golden eagles, moose, and a canyon packed with wildlife

The canyon holds mule deer, bighorn sheep, moose, elk and black bears, and the varied terrain gives each species its own zone.

Three distinct habitats run through the park: conifer forest, arid sagebrush, and the riparian corridor along the river. Golden eagles and red-tailed hawks nest in the canyon cliffs above it all.

Birdwatchers can find green-tailed towhees, Bullock’s orioles and Cassin’s finches in the brush and trees. Dawn and dusk are when the animals move most, so those are the windows worth planning around.

Meet the ferrets teaching visitors about extinction and survival

The visitor center runs from 10 a.m. to 5 p.m., May 22 through Sept. 7, and inside you’ll find interactive exhibits covering the canyon’s ecology, geology and wildlife.

In 2024, the park brought in two domestic ferrets from the U.S. Fish and Wildlife Service’s breeding facility in Colorado.

They’re there to represent the black-footed ferret, one of North America’s most endangered species, which was once thought to be completely extinct until a small group turned up in Meeteetse, Wyoming, in 1981.

The ferrets appear at the visitor center during the summer and during special park programs.

Camp free under certified dark skies, or stay in a heated yurt

The park has two campgrounds: Sawmill and Popo Agie, both with primitive tent and small camper sites. You’ll find vault toilets, seasonal water pumps, fire pits and picnic tables.

If you want a roof, the park rents heated yurts that stay open through winter. Up above the canyon, Worthen Meadow Reservoir adds more camping options and trail access.

The park charges no entry fee. That’s not a typo.

Camping fees apply, but walking in and spending the day costs you nothing, which is rare for a park this good.

Visit Sinks Canyon State Park in Wyoming

Sinks Canyon State Park sits six miles southwest of Lander, Wyoming, off Highway 131. Entry is free, and the drive from Lander takes about 10 minutes.

The visitor center runs seasonally, 10 a.m. to 5 p.m. from May 22 through Sept. 7 in 2026. Camping fees apply at both campgrounds; check the official website for current rates and yurt availability.

Lander has restaurants, grocery stores and lodging if you need a base. Bring layers; the canyon sits high enough that mornings run cold even in summer.

This article was created with AI assistance and human editing.

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