California nears completion of the world’s largest wildlife crossing along Highway 101

On a stretch of Highway 101 where headlights never really stop, California is finishing a project that tries to stitch wild country back together over eight roaring lanes of traffic. The Wallis Annenberg Wildlife Crossing is rising at Liberty Canyon in the city of Agoura Hills, turning a notorious roadkill corridor into a living bridge of soil, rock, and native plants. If it works the way biologists hope, it will reconnect the Santa Monica Mountains to the rest of the region and give everything from mule deer to mountain lions a safer way across.

For those of us who spend a lot of time outside, this is more than a flashy piece of infrastructure. It is a test of whether a state carved up by freeways can still function as real habitat, not just a patchwork of isolated parks. As the crossing nears completion, the story behind it says a lot about how far California is willing to go to keep its wildlife on the landscape.

Where the crossing sits and why this canyon matters

The Wallis Annenberg Wildlife Crossing is being built directly over the 101 in the city of Agoura Hills in Los Angeles County, at a spot long known to biologists as Liberty Canyon. On a map, this is the narrow throat between the Santa Monica Mountains to the south and larger open spaces to the north, a natural funnel where animals have tried to cross the freeway for decades. According to Caltrans, the project is formally listed as the US-101 – Wallis Annenberg Wildlife Crossing at Liberty Canyon, with the Location described as In the Agoura Hills in Los Angeles County, a reminder that this is not some remote overpass but a wild lifeline in the middle of a metro area.

Stand on the nearby ridges and you can see why this spot was chosen. To the south, the protected core of the Santa Monica Mountains stretches toward the Pacific. To the north, open space and mountain habitat continue toward the Simi Hills and beyond. The problem is the 101, a concrete barrier that has turned what should be one continuous ecosystem into fragments. A quick look at the Liberty Canyon area shows how close the habitat patches are, and how completely the freeway slices between them.

How the project grew from local concern to global model

The idea of a wildlife bridge at Liberty Canyon started with local biologists and residents watching animals die on the 101 and realizing the Santa Monica Mountains were slowly turning into an island. Over time, that concern hardened into a campaign that pulled in conservation groups, scientists, and eventually state agencies. The nonprofit partners behind the effort built out a detailed vision on the 101wildlifecrossing site, explaining how a vegetated overpass could reconnect core habitats and support regional biodiversity instead of letting the mountains’ wildlife fade out in isolation.

What began as a regional push eventually caught the attention of California leaders, who framed the crossing as part of a broader strategy to keep wildlife moving in a state crisscrossed by freeways. In an update from Jun, the state described how California had entered the final phase of construction on what it calls the world’s largest wildlife crossing, signaling that this is no longer a niche experiment but a flagship project for the state.

What “world’s largest wildlife crossing” actually means

Plenty of overpasses carry animals over roads, from elk bridges in Wyoming to toad tunnels under rural lanes, but the Wallis Annenberg Wildlife Crossing is being built on a different scale. State officials have repeatedly described it as the largest wildlife crossing in the world, a claim echoed in public outreach that notes The Wallis Annenberg Wildlife Crossing will be the largest wildlife crossing in the world and is expected to be completed by fall 2026. That description appears in a project update shared by Wallis Annenberg Wildlife campaign, which has leaned into the scale of the bridge as a way to draw attention to the stakes.

Size here is not just about bragging rights. Spanning the full width of the 101 and associated lanes means the structure has to be wide and deep enough to feel like real habitat, not a narrow concrete shelf. State briefings describe a vegetated superstructure that will be built over the freeway, with enough soil depth to support mature shrubs and small trees. Engineering coverage notes that the vegetated superstructure is a defining feature, designed so that an animal stepping onto the bridge experiences continuous ground cover instead of a jarring, exposed crossing.

Construction progress and the push toward a 2026 opening

From the highway, the crossing already looks like a massive concrete saddle stretching over the 101, but the work that matters most to wildlife is still underway. The state announced in Jun that California had entered the final phase of construction, with the project expected to be completed by fall 2026, and that milestone marked the shift from heavy structural work to the more detailed tasks of waterproofing, backfilling, and planting. In that update, officials emphasized that Today marked the start of that last big push, with an eye toward getting animals on the bridge as soon as it is safe.

More recently, state communications have sharpened the timeline. An early Feb briefing said California is closing in on completion and reiterated that the bridge is expected to open by the end of 2026, while also highlighting the ecological features that still need to be installed. That same update noted that the bridge will feature coastal sage scrub plant species native to the Santa Monica Mountains, which means the final months of work will be as much about soil mixes and irrigation lines as about cranes and rebar.

Delays, weather, and why the schedule slipped

Anyone who has watched a big project go up in Southern California will not be surprised that the crossing is behind its original schedule. When ground was broken in 2022, the project was expected to be completed in 2025, but that target did not survive two consecutive years of record rain and flooding in Los Angeles County. A local report on concerns about the bridge spelled it out clearly, noting that When ground was broken in 2022, the project was expected to be completed in 2025. But two years of record rain and flooding in Los Angeles County slowed work and complicated the relocation of utility lines that had to be moved before the bridge could be fully built.

Project updates shared in Jan echoed that reality, explaining that What will eventually be the largest wildlife crossing in the world is running behind schedule and over budget due to a host of factors, including weather and construction challenges. One widely shared project brief noted that construction is expected to be completed in late 2026, describing the crossing as Infrastructure That Saves while acknowledging that the timeline had slipped. More recently, a detailed look at the site quoted Rock, a key project voice, saying the new completion date in November or early December is “aggressive but doable” now that utility moving is complete and the bridge’s hollow interior can be filled with concrete, a sign that the team believes the worst delays are behind them, as reported in the Rock interview.

Price tag, funding gaps, and new money to finish the job

Big concrete and steel do not come cheap, especially when you are building over an active freeway. Early coverage of the project put the cost at $92-million, describing it as a $92-million effort slated for completion in 2026. That figure appeared in an overview of the crossing that noted the structure would sit Above the US-101 Freeway in Agoura Hills, carrying soil and vegetation from one side of the freeway to the other. The same report pointed out that the first phase of construction had already been completed and that the crossing was expected to open in 2026, underscoring how much money and time had already been sunk into the work $92.

Since then, the budget has climbed. A recent funding decision by a state transportation body noted that the Commission has allocated $18.8 million to the Wallis Annenberg Wildlife Crossing, in partnership with the California Department of Transportation, and that the total project cost has swelled to $114 million. That allocation, described as $18.8 million, is meant to close remaining funding gaps and keep the schedule on track. For hunters, anglers, and anyone who cares about functioning habitat, the price tag is steep, but it reflects the reality of building a massive, vegetated bridge in the middle of one of the busiest corridors in the state.

Traffic closures and what drivers see on the ground

While the crossing is being built for wildlife, people in Agoura Hills have been living with the day to day impacts of construction. Caltrans announced that beginning in September, the section of Agoura Road near the project would Close for Wildlife Crossing Construction, with weekday closures from 7 a.m. to 5 p.m. and the possibility of additional closures on weekends and holidays. That notice, which described the work as Construction of the Wallis Annenberg Wildlife Crossing in Agoura Hills, emphasized that the temporary pain for drivers would help reconnect habitats and support regional biodiversity once the bridge is finished, as laid out in the Agoura Road closure notice.

Drivers on the 101 have watched the bridge take shape in stages, from drilled shafts and columns to the massive concrete arches that now span the freeway. A technical overview of the project noted that construction of the first phase, including the structural supports, had been completed, and that crews were moving into the construction of the vegetated superstructure that will eventually hide the concrete under soil and plants. That same engineering summary described how the project broke ground in the middle of 2022 but faced two consecutive years of heavy rain that complicated work, a reminder that the construction story here is as much about weather and logistics as about wildlife.

What the finished bridge will look and feel like to wildlife

When the last crane leaves Liberty Canyon, the crossing will not look like a typical overpass. The plan is to bury the structure under deep soil, then plant it with coastal sage scrub and other native species so that, from an animal’s perspective, it feels like a natural saddle between hills. State descriptions say the bridge will feature coastal sage scrub plant species native to the Santa Monica Mountains, with the goal of matching the surrounding habitat as closely as possible. That detail, highlighted in the Feb update, matters because animals are far more likely to use a crossing that feels like familiar ground cover than a bare slab of concrete.

Lighting, noise, and fencing are being tuned with the same goal in mind. High walls and carefully designed barriers will funnel animals toward the bridge while blocking headlights and dampening traffic noise, and the approaches on both sides will be graded to create gentle slopes rather than steep ramps. A recent overview of the project’s ecological goals noted that the crossing is intended to support long term population viability for species that have been boxed in by the freeway, including predators that need large territories. That same summary said California is nearing completion of the Wallis Annenberg Wildlife Crossing and framed the bridge as a key piece of the state’s strategy to keep wildlife populations connected, as described in the California Governor briefing.