Its 12-square-mile (31 km2) watershed, the largest in Seattle, exhibits relatively dense biodiversity for an urban setting;[4] it is home to frogs, newts, ducks, herons, and beavers, in addition to more than 75,000 people.

[13] Thornton creek is home to many native species, muskrats, beavers, otters, bats, crayfish and coyotes, and in addition is an important breeding ground for great blue herons.

Building on gradual successes in restoration,[7][15] activist neighbors began[6][16] working with the City of Seattle and developers toward daylighting parts of the buried creek.

[17] In 2004, the City of Seattle purchased the 2.4-acre (0.97 ha) parking lot from Northgate Mall and began building the Thornton Creek Water Quality Channel.

[18] Organizations of citizens have cleaned up nearby wetlands, educated the public about stream health and quality of neighborhood life, and rallied to bring more of the creek to daylight.