The Sacramento NWR Complex was created in an attempt to resolve the conflict between the needs of migrating birds using the Pacific Flyway, and those of agriculture.

By the beginning of the 20th century, much of this had been replaced by farmland, particularly for the growing of rice, and the rivers no longer create new wetlands because their flow is controlled by levees and irrigation schemes.

In 1937, the United States Fish and Wildlife Service, with the aid of the Civilian Conservation Corps, began the process of creating a refuge within dry, alkaline lands between the towns of Willows and Maxwell.

The water flows in the refuge have to be controlled artificially, and the vegetation has to be managed actively through irrigation and burning, to ensure that the wetlands remain productive, and provide adequate food and resting places for the birds.

Among those most likely to be seen by visitors (depending on season) are: The Sacramento National Wildlife Refuge Complex boasts a diverse flora, even though large amounts of the historic wetland has been destroyed.