California's 4th congressional district
Interactive map of district boundaries since 2023 (Used in the2022 elections)
Representative	Mike Thompson D–St. Helena
Population (2024)	760,875[1]
Median household income	$98,067[2]
Ethnicity	51.3%White 31.4%Hispanic 7.6%Asian 5.3%Two or more races 2.8%Black 1.6% other
Cook PVI	D+17[3]

California's 4th congressional district is aU.S. congressional district inCalifornia. The district is located in the northwestern part of the state, and includes all ofLake County andNapa County, most ofYolo County, and parts ofSolano County andSonoma County. Major cities in the district includeDavis,Woodland,Napa,Vacaville, and most ofSanta Rosa. The district is solidlyDemocratic, and is represented byMike Thompson.^[1]

From 2013 to 2023, the district encompassed theSierras fromTruckee to theSequoia National Forest, as well as a largely suburban area on the edge of theSacramento Valley in southwesternPlacer County. It consisted ofAlpine,Amador,Calaveras,El Dorado,Mariposa, andTuolumne counties plus most ofPlacer County and portions ofFresno,Madera, andNevada counties. The district was represented byRepublicanTom McClintock.^[4]

In 2006,Republicans had 48 percent of voter registrations,Democrats had 30 percent, andLibertarians had roughly 5 percent.^[5] A Democratic congressional candidate nearly won the district in 2008, losing by only half a percentage point and less than 1,600 votes, indicating that the district was much more competitive than it appeared to be.

New district boundaries for the 2012 elections shifted the population center to the south and east. Registered Democrats and Independents/Decline to State voters in the new district area outnumber registered Republicans by 12%. However, Republicans, Independents/Decline to State, and small third parties outnumber Democrats well over a 2 to 1 ratio. There were 183,800 Republicans, 117,300 Democrats, and 97,200 others.^[6] In presidential elections,Donald Trump won the district in2016 with 54% of the vote and won in2020 with 53.7% of the vote. In the 2018 and 2020 elections, the Republican candidate won over 53% of the vote.^[7]

In the 2020 redistricting, the district was shifted again to the San Francisco Bay Area. It includes all ofLake County andNapa County, most ofYolo County, and parts ofSolano County andSonoma County. Major cities in the district includeDavis,Woodland,Napa,Vacaville, and most ofSanta Rosa. The new 4th district is solidlyDemocratic, and is represented byMike Thompson.^[1]

Under the 2020 redistricting, California's 4th congressional district encompassesLake,Napa, andYolo Counties, and parts ofSonoma andSolano Counties. The area in Sonoma County includes the cities ofSanta Rosa,Rohnert Park,Sonoma,Petaluma, andCotati; and the census-designated placesBoyes Hot Spring,El Verano,Penngrove,Sonoma State University,Kenwood,Glen Ellen,Eldridge,Fetters Hot Springs-Agua Caliente, andTemelec. The area in Solano County includes the cities ofVacaville,Dixon, andRio Vista; and the census-designated placesHartley andAllendale.

Sonoma County is split between this district and the2nd district. They are partitioned by Petaluma River, Highway 116, Redwood Highway, Robber Rd, Petersen Rd, Llano Rd, S Wright Rd, W College Ave, Jennings Ave, Administration Dr, Bicentennial Way, Cleveland Ave, Old Redwood Highway, Cross Creek Rd, Sonoma Highway, and Sonoma Creek.

Solano County is split between this district and the8th district. They are partitioned by Soda Springs Rd, Union Pacific, Alamo Dr, Leisure Town Rd, Hawkins Rd, Bay Area Exxextric, Shilo Rd, Collinsville Rd, and Montezuma Slough.

• Santa Rosa – 178,127
• Vacaville – 102,386
• Napa – 77,480
• Davis – 66,850
• Woodland – 61,032
• Petaluma – 59,776
• West Sacramento – 53,519
• Rohnert Park – 44,390
• American Canyon – 21,837
• Dixon – 18,988
• Clearlake – 16,685
• Sonoma – 11,024
• Rio Vista – 10,217

• University of California, Davis – 8,525
• Cotati – 7,584
• Winters – 7,195
• Hidden Valley Lake – 6,235
• Boyes Hot Springs – 6,215
• St. Helena – 5,438
• Calistoga – 5,228
• Lakeport – 5,026
• Penngrove – 4,172
• Fetters Hot Springs-Agua Caliente – 4,144
• El Verano – 3,867
• Yountville – 3,436
• Kelseyville – 3,382
• Clearlake Riviera (Kelseyville Riviera) – 3,410
• North Lakeport – 3,314
• Esparto – 3,108
• Lucerne – 3,067
• Esparto – 2,877
• Nice – 2,731
• Sonoma State University – 2,679
• Angwin – 2,633
• Clearlake Oaks – 2,551
• Hartley – 2,510

Member	Party	Dates	Cong ress	Electoral history	Counties
District created March 4, 1873
Sherman Otis Houghton (San Jose)	Republican	March 4, 1873 – March 3, 1875	43rd	Redistricted from the1st district andre-elected in 1872. lost re-election.	Fresno,Inyo,Kern,Los Angeles,Mariposa,Merced,Mono,Monterey,San Bernardino,San Diego,San Luis Obispo,San Mateo,Santa Barbara,Santa Clara,Santa Cruz,Stanislaus,Tulare,Ventura
Peter D. Wigginton (Merced)	Democratic	March 4, 1875 – March 3, 1877	44th	Elected in 1875. Retired.
Romualdo Pacheco (San Luis Obispo)	Republican	March 4, 1877 – February 7, 1878	45th	Lost contested election.
Peter D. Wigginton (Merced)	Democratic	February 7, 1878 – March 3, 1879		Won contested election. Retired.
Romualdo Pacheco (San Luis Obispo)	Republican	March 4, 1879 – March 3, 1883	46th 47th	Elected in 1879. Re-elected in 1880. Retired.
Pleasant B. Tully (Gilroy)	Democratic	March 4, 1883 – March 3, 1885	48th	Elected in 1882. Retired.	San Francisco
William W. Morrow (San Francisco)	Republican	March 4, 1885 – March 3, 1891	49th 50th 51st	Elected in 1884. Re-elected in 1886. Re-elected in 1888. Retired.
John T. Cutting (San Francisco)	Republican	March 4, 1891 – March 3, 1893	52nd	Elected in 1890. Retired.
James G. Maguire (San Francisco)	Democratic	March 4, 1893 – March 3, 1899	53rd 54th 55th	Elected in 1892. Re-elected in 1894. Re-elected in 1896. Lost re-election.
Julius Kahn (San Francisco)	Republican	March 4, 1899 – March 3, 1903	56th 57th	Elected in 1898. Re-elected in 1900. Lost re-election.
Edward J. Livernash (San Francisco)	Democratic/ Union Labor	March 4, 1903 – March 3, 1905	58th	Elected in 1902. Lost re-election.
Julius Kahn (San Francisco)	Republican	March 4, 1905 – December 18, 1924	59th 60th 61st 62nd 63rd 64th 65th 66th 67th 68th	Elected in 1904. Re-elected in 1906. Re-elected in 1908. Re-elected in 1910. Re-elected in 1912. Re-elected in 1914. Re-elected in 1916. Re-elected in 1918. Re-elected in 1920. Re-elected in 1922. Re-elected in 1924. Died.
Vacant		December 18, 1924 – February 17, 1925	68th
Florence Prag Kahn (San Francisco)	Republican	February 17, 1925 – January 3, 1937	68th 69th 70th 71st 72nd 73rd 74th	Elected to finish husband's term. Re-elected in 1926. Re-elected in 1928. Re-elected in 1930. Re-elected in 1932. Re-elected in 1934. Lost re-election.
Franck R. Havenner (San Francisco)	Progressive	January 3, 1937 – January 3, 1939	75th 76th	Elected in 1936. Re-elected in 1938. Lost re-election.
	Democratic	January 3, 1939 – January 3, 1941
Thomas Rolph (San Francisco)	Republican	January 3, 1941 – January 3, 1945	77th 78th	Elected in 1940. Re-elected in 1942. Lost re-election.
Franck R. Havenner (San Francisco)	Democratic	January 3, 1945 – January 3, 1953	79th 80th 81st 82nd	Elected in 1944. Re-elected in 1946. Re-elected in 1948. Re-elected in 1950. Lost re-election.
William S. Mailliard (San Francisco)	Republican	January 3, 1953 – January 3, 1963	83rd 84th 85th 86th 87th	Elected in 1952. Re-elected in 1954. Re-elected in 1956. Re-elected in 1958. Re-elected in 1960. Redistricted to the6th district.
Robert Leggett (Vallejo)	Democratic	January 3, 1963 – January 3, 1979	88th 89th 90th 91st 92nd 93rd 94th 95th	Elected in 1962. Re-elected in 1964. Re-elected in 1966. Re-elected in 1968. Re-elected in 1970. Re-elected in 1972. Re-elected in 1974. Re-elected in 1976. Retired.	1963–1967 Colusa,Glenn,Lake,Solano,Sutter,Yolo,Yuba
					1967–1973 Colusa,Glenn,Lake,Sacramento (outsidethe city),Solano,Sutter,Yolo,Yuba
					1973–1975 Colusa,Glenn,Solano, southwesternSacramento,Sutter,Yolo,Yuba
					1975–1983 Colusa, westernSacramento,Solano,Sutter,Yolo
Vic Fazio (West Sacramento)	Democratic	January 3, 1979 – January 3, 1993	96th 97th 98th 99th 100th 101st 102nd	Elected in 1978. Re-elected in 1980. Re-elected in 1982. Re-elected in 1984. Re-elected in 1986. Re-elected in 1988. Re-elected in 1990. Redistricted to the3rd district.
					1983–1993 Sacramento (outside thecity),Solano,Yolo
John Doolittle (Roseville)	Republican	January 3, 1993 – January 3, 2009	103rd 104th 105th 106th 107th 108th 109th 110th	Redistricted from the14th district andre-elected in 1992. Re-elected in 1994. Re-elected in 1996. Re-elected in 1998. Re-elected in 2000. Re-elected in 2002. Re-elected in 2004. Re-elected in 2006. Retired.	1993–2003 Alpine,Amador,Calaveras,El Dorado,Mono,Placer, northeasternSacramento,Tuolumne
					2003–2013 EasternButte,El Dorado,Lassen,Modoc,Nevada,Placer,Plumas,Sacramento (Orangevale),Sierra
Tom McClintock (Elk Grove)	Republican	January 3, 2009 – January 3, 2023	111th 112th 113th 114th 115th 116th 117th	Elected in 2008. Re-elected in 2010. Re-elected in 2012. Re-elected in 2014. Re-elected in 2016. Re-elected in 2018. Re-elected in 2020. Redistricted to the3rd district.
					2013–2023 Eastern central California includingLake Tahoe,Roseville, andYosemite National Park
Mike Thompson (St. Helena)	Democratic	January 3, 2023 – present	118th 119th	Redistricted from the5th district andre-elected in 2022. Re-elected in 2024.	2023–present Lake,Napa, most ofYolo, parts ofSolano andSonoma

In 2018, six Democratic candidates filed statements of candidacy with theFederal Election Commission (FEC).^[61] They were, in alphabetical order by last name:Regina Bateson;Roza Calderon; Richard Martin; Robert Lawton;Jessica MorseArchived July 28, 2017, at theWayback Machine; andRochelle Wilcox. Martin and Wilcox^[62] dropped out of the race, with Wilcox^[63] endorsing Morse in February.

Retired Air Force Lieutenant Colonel Charlie Brown, who was the Democratic nominee for this seat in2006 and2008, was "seriously considering" running in 2018,^[64] but decided in June 2017 against a third campaign. In January 2018, Brown endorsed Morse for the nomination.^[65] Bob Derlet,^[66] the Democratic nominee in2016, also endorsed Morse in January.

On the Republican side, McClintock had one challenger,Mitchell Kendrick WhiteArchived March 2, 2018, at theWayback Machine, who filed with the FEC in January.^[67]

In February, theCalifornia Democratic Party (CDP) endorsed^[68] Jessica Morse in a contested nomination. Roza Calderon was able to successfully collect 322 CDP-credentialed delegate signatures needed to block the endorsement, in which Morse only received 44 delegate votes. However, CDP staff refused to accept the forms after it was alleged they closed doors early to prevent the submission. A petition was later filed with the Compliance Review Commission (CRC)^[69] by Calderon. The CRC voted to accept and count the signatures, ultimately disqualifying enough signatures to proceed with Morse's endorsement.

California allows candidates to include their professional description under their names on the ballot. Regina Bateson challenged Morse's ballot designation title of "National Security Fellow" at the Sacramento Superior Court after months of controversy that Morse was "fluffing" her credentials.^[70] California's Secretary of State,Alex Padilla, struck down Morse's three ballot designations before Judge Gevercer ruled^[71] that she presented "no credible evidence" to use the ballot designation of "National Security Fellow". Instead, he held that this title would mislead the average person about her recent activities. In the official Certified Candidate List for the primary election,^[72] Morse's ballot designation was left blank.

Under the Californianonpartisan blanket ("jungle") primary system, only the two candidates with the most votes on June 5, regardless of party, went on to the general election on November 6. Two Republicans and four Democrats appeared on the primary ballot.^[68] Morse finished second, qualifying for the general election ballot, along with McClintock.

For the November ballot, Morse was also denied "National Security" as her designation.^[73] In the November general election, McClintock held the district with an advantage of more than eight percentage points.^[74]

• List of United States congressional districts

• California's congressional districts

• GovTrack.us:California's 4th congressional district
• California Citizens Redistricting Commission:wedrawthelines.ca.gov 2012 final district maps

38°18′N119°42′W / 38.3°N 119.7°W /38.3; -119.7

• Congressional districts of California
• Government of Lake County, California
• Government of Napa County, California
• Government of Solano County, California
• Government of Sonoma County, California
• Government of Yolo County, California
• Constituencies established in 1873
• 1873 establishments in California

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