The Rim of the Valley is a campaign to expand the Santa Monica Mountains National Recreation Area by over 190,000 acres, more than doubling the size of the existing park. The expansion will enable the National Park Service and local communities to better protect natural resources and habitats, and provide improved access to nature for recreational and educational purposes. In particular, the expansion will enhance management of dwindling habitat, active wildlife corridors, and historic watersheds critical to the Los Angeles region's ecosystem, one of the few areas where large carnivores such as the mountain lion still roam the hills adjacent to a bustling metropolis.

If successful, the expansion will be among the region's most significant conservation accomplishments since the founding of the original park in 1978. Currently, NPCA is working with local elected officials, conservation groups, community and faith-based organizations, and numerous other constituencies to build support for legislative protection for the Rim of the Valley.