Oso Creek Trail began in April 1997 as a community collaboration in Mission Viejo, where volunteers gather in late spring to celebrate the Earth and the arts. Nestled along the riparian corridor of Oso Creek Valley, it connects residences to city facilities, the commercial core, and surrounding neighborhoods while serving as part of a backbone city trail system intended to benefit future generations. Developed with amenities that educate and honor the community, it includes the Peace Obelisk honoring victims of 9/11, the mosaic history walls in the Character Garden, painted butterflies, the Celebration Garden, the Wave Wall on the Upper Oso Creek Trail, and murals around the Village Green. The trail functions as a walking garden and gathering place, and the creek and trail system expose users to local plant and animal life and the working ecosystem. Oso Creek flows from north of the Santa Ana Mountains, joins Trabuco Creek, and ultimately reaches the Pacific Ocean. The Oso Creek Valley also yielded and preserved rare fossils, including baleen and toothed whales, long-snouted dolphins, primitive sea lions, sharks, rays, and bony fish. After grading was completed, the creek was engineered to carry increased storm water, and reclaimed water lines were installed along its eastern side to move recycled water from the Upper Oso Reservoir to Mission Viejo residential areas for landscape beautification. The creek edge was replanted with indigenous riparian species including coyote bush, mulefat, Mexican elderberry, toyon, and willows, and over time shifting vegetation has helped bring back more wildlife such as house finches, song sparrows, goldfinches, Costa's hummingbirds, turtles, great blue herons, and great egrets. Created with both riparian and drought-tolerant plant material sustained with minimal irrigation, the trail includes over 60 plant varieties, with the California sycamore as a significant tree alongside the coast live oak and olive tree. Most of Mission Viejo lies in the 133.9-square-mile San Juan Creek watershed, with Oso Creek serving as the main route by which water travels toward the ocean. Once dry for much of the year, the creek now flows year-round largely because of human activities such as over-irrigation and residential car washing, and this water carries pollutants including pet waste, litter, bacteria, fertilizer, and pesticides through the storm drain system to the ocean. In the late 1970s, the Oso Creek Barrier and Return Water Pump Station was installed just north of Oso Parkway to capture dry-weather creek flow and send it to the Upper Oso Reservoir for storage and later use, mostly to irrigate city-owned landscaped areas, and more than 70% of Mission Viejo's landscaped areas are now irrigated with reclaimed water.