A concrete bridge the length of two football fields now spans 10 lanes of one of America's busiest freeways — and it was built entirely for animals that can't read a map.

  • 10 freeway lanes spanned by a single crossing structure
  • 6,000 native plants already rooted on top of the bridge
  • 41% of documented mountain lion matings since 2002 have been between close relatives
  • Dec. 2, 2026 scheduled opening date, after roughly seven years of construction

The Wallis Annenberg Wildlife Crossing, in Agoura Hills northwest of Los Angeles, is designed to reconnect the Santa Monica Mountains to the Simi Hills and beyond, giving the area's boxed-in mountain lion population somewhere new to roam. A bridge already stretches across the 101 Freeway; crews recently finished a second overpass over adjacent Agoura Road, and the remaining job is filling the gap between road and freeway with millions of cubic feet of soil to create one continuous animal pathway, according to the Los Angeles Times.

Why the Freeway Became a Cage

Mountain lions in the Santa Monica Mountains have been boxed in by highways on nearly every side for decades, unable to disperse to find mates outside their own shrinking gene pool. Seth Riley, wildlife branch chief for the Santa Monica Mountains National Recreation Area, says 41% of documented matings in an ongoing National Park Service study have been between close relatives — and researchers have already photographed a young male with a kinked tail, a physical sign of inbreeding. Without intervention, Riley says modeling shows "essentially a 100% chance of extinction" for the local population within 50 years.

That's the problem the crossing was built to solve. More than 25 years of NPS tracking data on collared lions helped pinpoint Liberty Canyon, the crossing's location, as the one remaining pinch point where animals still occasionally attempt the crossing on foot — and often don't survive it.

What's Left Before Opening Day

The bridge deck is already landscaped with native shrubs and grasses meant to muffle headlights and freeway noise, and sound walls line both sides to keep animals calm as they cross. The last major task is soil compaction, a slow, weather-dependent process: the clay- and silt-rich ground becomes dangerously slick when wet, which is why an approaching El Niño pattern is the project's biggest remaining risk.

Beth Pratt, president of the Wildlife Crossing Fund and the project's public face, has weathered years of online criticism over its cost and delays.

"I keep saying, 'Mother Nature, we're trying to help you. Let's not throw any more complications our way.'"

Once open, the crossing won't just serve mountain lions — bobcats, coyotes, deer and smaller species are all expected to use it, turning a decades-old barrier into the single biggest connective fix in the region's wildlife corridor. Riley says it isn't too late for the local lion population to recover: the soon-to-open bridge will let the Santa Monica Mountains' big cats seek mates in the Simi Hills and beyond, loosening a genetic bottleneck that has been tightening since the 101 Freeway first cut through the landscape generations ago.