Currently, the 4th district encompasses the Sierra from Truckee to the Sequoia National Forest. It consists of Alpine, Amador, Calaveras, El Dorado, Mariposa, and Tuolumne counties plus portions of Fresno, Madera, Nevada, and Placer counties.
Prior to redistricting by the California Citizens Redistricting Commission of 2011, the 4th district encompassed the northeast corner of the state, stretching from the eastern suburbs of Sacramento north to the Oregon border. It consisted of El Dorado, Lassen, Modoc, Nevada, Placer, Plumas, and Sierra counties plus portions of Butte and Sacramento counties.
To learn more, visit: https://statisticalatlas.com/congressional-district/California/District-4/Overview