Somewhere in the Santa Monica Mountains, a mountain lion is waiting. Not patiently — mountain lions don't wait — but instinctively pressing against the edge of its territory, sensing the forest beyond the roaring river of traffic it cannot cross. By the end of 2026, for the first time in decades, there will be a way across.
The **Wallis Annenberg Wildlife Crossing** at Liberty Canyon in Agoura Hills, California, is now in its final phase of construction. When complete, it will be the **largest wildlife crossing ever built on Earth** — a 210-foot-wide, 174-foot-long bridge arching over 10 lanes of U.S. Highway 101, covered entirely in native California vegetation, designed to be indistinguishable from the natural landscape around it.
**Why a Bridge for Animals**
The 101 Freeway cuts directly through the habitat of Southern California's mountain lions — splitting the Santa Monica Mountains from the Simi Hills and Sierra Madre range, effectively stranding a small population of big cats on either side.
The consequences have been profound. Genetic studies found that the Santa Monica Mountains mountain lions are among the **most genetically isolated large carnivore populations anywhere in the world** outside of the Florida panther. Inbreeding is already affecting the population. Without new genetic exchange, local extinction is a realistic possibility within decades.
It's not just mountain lions. Bobcats, mule deer, coyotes, foxes, and hundreds of smaller species — reptiles, insects, small mammals — are equally trapped by the freeway. A road doesn't just kill animals that try to cross it. It fragments entire ecosystems, severing the movement that healthy wildlife populations depend on.
**The Crossing by the Numbers**
- **Width:** 210 feet (64 metres) — wide enough for a shy mountain lion to cross without feeling exposed - **Length:** 174 feet (53 metres) — spanning all 10 lanes of the 101 - **Coverage:** Native California plants, soil, rocks, trees, and brush - **Camera network:** Motion-triggered cameras will document every crossing - **Cost:** Approximately $90 million, funded by private philanthropy and public conservation funds - **Expected opening:** Late 2026
The width is the critical factor. Mountain lions have been observed at the site's perimeter but won't cross unless they feel concealed. At 210 feet, the Annenberg Crossing is wide enough that a mountain lion in the middle genuinely cannot see the cars on either side. It's designed to feel like forest, not like a bridge.
**A Decade of Work**
The project began with a scientific paper in 2002 that identified the Highway 101 crossing point as the single most important wildlife corridor opportunity in Southern California. It took 20 more years of advocacy, fundraising, and design before construction began — on Earth Day 2022.
The **Wallis Annenberg Foundation** provided the largest single donation — $25 million — with additional support from the California Department of Transportation, the National Wildlife Federation, and dozens of other organisations.
**The Mountain Lion Who Started Everything**
There's a mountain lion named **P-22** who became famous in Los Angeles — photographed in Griffith Park, he was the rare individual who crossed both the 101 and the 405 freeways and survived. He lived alone for a decade in an urban park, unable to find a mate, unable to leave. He died in 2022.
P-22's story made Angelenos understand what the freeway meant for wildlife — not just as a danger, but as a prison. The outpouring of grief when he died accelerated fundraising for the Annenberg Crossing. He is, in a very real sense, the reason this bridge is being built.
The mountain lions who cross it won't know his name. But they will benefit from what his story made possible.
A long road. And now, finally, a crossing. 🦁🌉
*Sources: California Governor's Office · California Department of Transportation · Los Angeles Times (January 26, 2026) · National Wildlife Federation · Wallis Annenberg Foundation*