I count 11 Walnut related businesses near Yuba City, right below the Oroville Dam:

https://www.walnuts.org/walnut-industry/handler-list/

Consider this, from Politico:

John Podesta, Center for American Progress: “I am going to my condo in Truckee [Calif.], like I do every year — will sit on my porch and do conference calls 50 feet from where the Donner Party ate each other.”

Source: http://www.politico.com/story/2009/06/where-dcs-a-listers-go-for-vacation-023151

Truckee, CA is an hour drive from Yuba City, a major walnut growing area.