A map of the Delta created by the US Geological Survey in the 1910s.
The Sacramento-San Joaquin River Delta provides drinking water for more than 25 million people, and irrigation for millions of acres of farm land. But our heavy use of the Delta has compromised its ecosystem. Scientists are keen to restore some of it, but there's no one alive today who remembers what the Delta looked like before we transformed it. That's where archival materials from the 19th century come in. Reporter: Lauren Sommer