What makes Southern California such an alluring place to live in is the way the city blends with nature. Residences and streets pop out among the mountains, valleys, canyons, and creeks, offering a continuous respite from urban life. Sadly, this has often meant a disruption for the local animals, who see their habitats torn apart by highways and are often at risk of being run over when trying to get around. The Wallis Annenberg Wildlife Crossing, which is under construction, hopes to finally fix this. Now, the team behind it just hit a major milestone.
Set to become the world’s largest wildlife overpass, the Wallis Annenberg Wildlife Crossing, is currently being built over the 101 Freeway in Agoura Hills, located 35 miles northwest of Downtown Los Angeles. When finished, it will unite the Santa Monica Mountains with the Simi Hills in the Santa Susana range. Construction began in April 2022, and the final horizontal girders were installed in May 2024. As it enters its final stage of construction, crews have begun laying nearly 5,000 native plants on the structure.
“The construction to date has really been about things like the rebar and the concrete, but we’re starting to put in for me what’s the important part, which is the nature on top of the freeway,” Beth Pratt, who is the regional executive director for the National Wildlife Federation, told KCLU. “We put the soil on (the crossing) earlier this year, and today, we’re putting the first native plants on top from the nursery, to start creating habitat for wildlife.”
To make sure the flora matched the surrounding landscape, a team collected seeds around the crossing. “It was a lot of work for our nursery team,” explained Pratt. “They started years ago. They gathered over a million hyperlocal seeds from a 5-mile radius, and have been growing them in our native plant nursery. I feel like I’ve watched these plants grow up, and today was graduation.”
The overpass has been thoroughly planned to attract the maximum amount of species. This includes mountain lions, bobcats, deer, bats, and birds, all with the mission to help boost a one-acre wildlife habitat. The project will also make the road safer for drivers, as Pew suggests wildlife overpasses can reduce collisions with fauna by up to 90%. If it all goes according to plan, the Wallis Annenberg Wildlife Crossing will be ready in fall 2026.
Crews have begun laying nearly 5,000 native plants on the Wallis Annenberg Wildlife Crossing, located northwest of Los Angeles.
A wildlife crossing over a Southern California highway is being planted with native plants to prepare as a nature-alike passage for local wildlife, including animals like mountain lions, to cross over safely pic.twitter.com/GtISe2bwpK
— Reuters (@Reuters) October 22, 2025
Slated to be completed in fall 2026, it will become the world’s largest wildlife overpass.
Some fun photos from our planting on the Wallis Annenberg Wildlife Crossing yesterday.
Taken by Jon Kopaloff/Getty Images. pic.twitter.com/n8UhmMxfQp
— Beth Pratt (@bethpratt) October 22, 2025
Sources: Another milestone for ambitious 101 Freeway wildlife crossing: First native plants go in; Milestone reached in the construction of the world’s largest wildlife crossing in the Conejo Valley
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