Cities in the district include Galt, Oakley, Lodi, Mountain House, and Stockton.

They are partitioned by Union Pacific, Highway 380, S Tracy Blvd, the California Aqueduct, S Banta Rd, Highway 5, Paradise Cut, S Manthey Rd, Walthall Slough, E West Ripon Rd, Kincaid Rd, Hutchinson Rd, and Stanislaus River.

The 9th district takes in the cities of Stockton, Tracy, Manteca, Lodi, Ripon, and Escalon and the census-designated places Mountain House, Terminous, Thornton, Collierville, Woodbridge, Acampo, Dogtown, Lockeford, Victor, Lincoln Village, Morada, Country Club, August, Garden Acres, Kennedy, Taft Mosswood, French Camp, Waterloo, Linden, Peters, Farmington, and Del Rio.

They are partitioned by Old River, Italian Slough, Western Farms Ranch Rd, Rankin Rd, Highway J14, Byron Hot Springs Rd, Camino Diablo, Kellogg Creek, Sellers Ave, Brentwood Blvd, Alloro Dr, Ghiggeri Dr, Emilio Dr, Guthrie Ln, Balfour Rd, Chestnut St, Byron Highway, Orwood Rd, Burlington Northern Santa Fe, Werner Dredger Cut, and Rock Slough.

The 9th district takes in the Woodward Reservoir, and the only census-designated place within it is Valley Home.