The 1st District stretches along the eastern edge of the state, from the Oregon border to the Mojave Desert. It includes most of the Mother Lode and Sierra Nevada Regions in addition to Lake Tahoe. However, because most of the district is rural, two-thirds of the district's population in 2000 lived in suburban Sacramento.
The 4th District covers a vast and predominantly rural region that includes 12 counties – Butte, Colusa, Del Norte, Glenn, Nevada (partly), Placer (partly), Shasta, Siskiyou, Sutter, Tehema, Trinity and Yuba Counties.