Sulphur Creek is a 4.5mi tributary of Aliso Creek in Orange County in the U.S. state of California. Draining about 6sqmi of mostly residential land in the southern San Joaquin Hills, it is Aliso Creek's largest tributary.Geologically the Sulphur Creek watershed was once part of a large and shallow sea that covered most of southern California. As the San Joaquin Hills rose and river sediments were deposited, land gradually emerged to form the present-day Orange County coast. Sulphur Creek is located in a crumpled, hilly area in the southern part of this range, formed differently from the continuous mountain chain to the north. Historically, being south of Aliso Creek, the Sulphur Creek watershed was part of the territory of the semi-nomadic Acjachemen Indian group, conquered by Spanish conquistadors in the 17th and 18th centuries and renamed the Juaneño by them.During the 19th century, the watershed became part of a rancho. In 1966, the creek was dammed to form Laguna Niguel Lake, while the surrounding hills were leveled as residential communities were constructed in the area following the '60s and '70s. The creek's basin eventually became part of the cities of Laguna Hills, Laguna Niguel, and a small portion in San Juan Capistrano. Increasing urban runoff in the 1960s caused most of the flow in the creek to be unnatural. The creek has since been channelized along most of its length to prevent floods from inundating the roads and houses that now line much of its banks.
