When it comes to states with the most wildlife overpasses and crossings, Colorado definitely leads the pack. As of 2025, the state has over 100 structures — including underpasses and overpasses — with more projects underway.
Colorado’s most recent wildlife overpass is the Greenland Wildlife Overpass along I-25, which also doubles as the largest wildlife overpass in the world.
According to Colorado Governor Jared Polis, the overpass was completed in less than a year, “ahead of schedule and on budget.”
“Colorado is leading the way in reducing wildlife-vehicle collisions and improving safety for both our motorists and wildlife,” Polis said in a statement. “The I-25 Greenland wildlife overpass is a momentous feat in our continued work to expand safe transportation options for both humans and wildlife, protecting critical habitat and our amazing outdoor spaces for generations to come.”
The area is home to huge swaths of migrating animals, including big game animals such as moose, bears, mountain lions, and more.
It’s also home to elk, mule deer, and pronghorn, who are notoriously distrustful of underpasses and enclosed tunnels. The overpass was designed with the hopes of enticing them to cross six lanes of highway safely.
And on June 20, six months after completion, the Greenland Overpass finally received its first elk visitors.
“The first elk have been recorded using the newly constructed Greenland Wildlife Overpass!” The Colorado Department of Transportation shared in a Facebook Post.
“The overpass was built through a partnership between CDOT, Colorado Parks and Wildlife, and Douglas County Government and is designed to improve wildlife connectivity and reduce the risk of wildlife-vehicle collisions.”
“These early crossings show the new structure is working! Check out as three elk make their way across the overpass.”
In the video, three elk can be seen picking their way along the bridge, which is 200 feet wide and 209 feet long, with gradually sloped entrances.
When it comes to size, the Greenland Wildlife Overpass won't be the biggest forever. After four years of construction — and 30 years of planning — California is currently nearing completion of the upcoming Wallis Annenberg Wildlife Crossing. The overpass, which is set to be finished in December 2026, will extend over a 10-lane urban freeway.
“You’re going to see this ecological transformation,” said Beth Pratt, California’s regional executive director for the National Wildlife Federation. “And that part of it is going to be over one of the busiest freeways in the world — that, to me, is just such a hopeful statement for what’s possible.”
“We can redeem a freeway.”
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Header image via Yellowstone National Park
