Sources: Homepages for the cities of Carson, Hawthorne and Inglewood and the Watershed Initiate Chapter of the Regional Water Quality Control Board.

The native residents of the Dominguez Watershed area were of the Shoshonian linguistic group who occupied the area as early as the 1500's until title to all land in California became vested in the King of Spain in 1769. When Mexico obtained title to California from Spain in 1822, the Sausal Redondo and Rancho San Pedro were formed in the area. Sausal Redondo consisted of approximately 22,460 acres and included the present-day cities of El Segundo, Gardena, Hawthorne, Hermosa Beach, Inglewood, Lawndale, Manhattan Beach, Playa Del Rey, Redondo Beach, and Torrance. It's owner, Don Antonio Avila used the land for grazing cattle. In 1860, Sir Robert Burnett of Scotland purchased Sausal Redondo from Avila's heirs. He expanded the sheep and cattle raising operations and planted thousands of eucalyptus, pepper, and fruit trees. Following the severe droughts or 1875 and 1876, Daniel Freeman, who purchased the land from Burnett, used the ranch for dry farming. By 1880, the area was producing a million bushels of barley a year.

The Rancho San Pedro, which came to be known as the Dominguez Ranch, began as a generous gift of 75,000 acres from the King of Spain to the Dominguez family in 1784. The vast Rancho spread from the Los Angeles River on the east, to the Pacific Ocean on the west. It encompassed what is now Torrance, Carson, Redondo Beach, and the LA Harbor. When the railroad was built between Los Angeles and the harbor in 1869, Manuel Dominguez donated land from the rancho for the new venture. In addition to the name Dominguez, many streets and businesses in the South Bay still bear witness to the Dominguez family. Manuel's daughters married into families with well recognized names such as Del Amo (recognized today by the giant Del Amo Fashion Center mall in Torrance), Watson (known today for the Watson Land Company and Industrial Centers) and Carson.

Historically, the area that now serves as the Los Angeles and Long Beach Harbors consisted of marshes and mudflats with a large marshy area, Dominguez Slough, to the north, and flow from the Los Angeles River entering where Dominguez Channel now drains. Near the beginning of the 20th century, channels were dredged, marshes were filled, wharves were constructed, the Los Angeles River was diverted, and a breakwater was constructed in order to allow deep draft ships to be directly offloaded and products swiftly moved. The Dominguez Slough was completely channelized in the mid 1900's in an effort to provide flood protection to much of the South Bay area. Eventually, two more breakwaters enclosed the greater San Pedro Bay and deep entrance channels were dredged to allow for entry of ships with need of 70 feet of clearance.