The State of Jefferson is a proposed U.S. state that would span the contiguous, mostly rural area of southern Oregon and Northern California, where several attempts to separate from Oregon and California, respectively, have taken place. The region encompasses most of Northern California's land but does not include San Francisco or other Bay Area counties that account for the majority of Northern California's population.

Northern California is a geographic and cultural region that generally comprises the northern portion of the U.S. state of California, spanning the northernmost 48 of the state's 58 counties. Its main population centers include the San Francisco Bay Area, the Greater Sacramento area, the Redding, California, area south of the Cascade Range, and the Metropolitan Fresno area. Northern California also contains redwood forests, along with most of the Sierra Nevada, including Yosemite Valley and part of Lake Tahoe, Mount Shasta, and most of the Central Valley, one of the world's most productive agricultural regions.