Since 2010, statewide droughts in California have further strained both Fresno County's and the entire Central Valley's water security.

[7][8] The area now known as Fresno County was the traditional homeland of Yokuts and Mono peoples, and was later settled by Spaniards during a search for suitable mission sites.

The original county seat was along the San Joaquin River in Millerton, but was moved to the rapidly growing town of Fresno on the newly built Southern Pacific Railroad line.

Floods caused immeasurable damage elsewhere and fires also plagued the settlers of Fresno County.

In 1882, the greatest of the early day fires wiped out an entire block of the city of Fresno, and was followed by another devastating blaze in 1883.

In 1865, William Helm brought his sheep to Fresno county, which was then a vast space of open land.

Anthony Easterby and Clovis Cole developed extensive grain and cattle ranches.

These and other citizens laid the groundwork for the cultivation of Fresno County – now one of the nation's leading agricultural regions.

[citation needed] The discovery of oil in the western part of the county, near the town of Coalinga at the foot of the Coast Ranges, brought about an economic boom in the 1900s (decade), even though the field itself was known at least as early as the 1860s.

[12] Fresno County consists of about 38 smaller towns including Fresno, Selma, Parlier, Clovis, Reedley, Sanger, Kerman, Kingsburg, Coalinga, Firebaugh, Calwa, Friant, Mendota, Fowler, Shaver lake, San Joaquin, Orange Cove, Del Ray, Yokuts Valley, Auberry, Huron, Caruthers, Riverdale, Laton, Big Creek, Tranquility, Biola, Raisin City, Easton, Three Rocks, Cantou Creek, Lanare, Minkler, Mayfair, Malaga, Bowles, Monmouth, and West Park.

In recent years, statewide droughts in California have further strained both Fresno's and the entire Central Valley's water security.

However, Fresno was named after two particular ash trees that grew near the town of Minkler on the Kings River, one of which is still alive and standing.

[citation needed] A number of minerals have been discovered in the county, including macdonaldite, krauskopfite, walstromite, fresnoite, verplanckite, muirite, traskite, and kampfite.

[citation needed] The racial makeup of Fresno County was 515,145 (55.4%) White, 49,523 (5.3%) African American, 15,649 (1.7%) Native American, 89,357 (9.6%) Asian (3.3% Hmong, 1.7% Asian Indian, 1.0% Filipino, 0.8% Laotian, 0.6% Chinese, 0.5% Japanese, 0.5% Cambodian, 0.3% Vietnamese, 0.2% Korean, 0.1% Pakistani, 0.1% Thai), 1,405 (0.2%) Pacific Islander, 217,085 (23.3%) from other races, and 42,286 (4.5%) from two or more races.

The department also provides law enforcement services by contract with the city of San Joaquin, population 4100.

Municipal police departments in the county are: Fresno, population 500,000; Clovis, 110,000; Sanger, 25,000; Reedley, 24,000; Selma, 23,000; Coalinga, 17,000; Kerman, 14,000; Kingsburg, 12,000; Huron, 7,000; Firebaugh, 8,500; Fowler, 6,500.

In 2020, Joe Biden became the first Democratic presidential candidate since Lyndon Johnson in 1964 to win a majority of the vote in Fresno County, only for Donald Trump to become the first Republican in 20 years to win the county just four years after Biden's victory.

Most smaller cities in Fresno such as Firebaugh, Selma, and Sanger are split, with Democratic-leaning urban centers and Republican-leaning exteriors.

[citation needed] Republicans have a plurality or majority of voter roll registration in the cities of Clovis, Coalinga, Kingsburg, Reedley, and the unincorporated areas.

From Fresno County's incorporation in 1856, it voted Democratic in every election until 1904, when President Theodore Roosevelt stood for re-election.

From 1932 to 1976, the county consistently voted Democratic, barring Richard Nixon's landslide victory over former Senator George McGovern (D-SD) in 1972.

With President Jimmy Carter's defeat by Ronald Reagan, Fresno became a GOP-leaning swing county.

On November 4, 2008, Fresno County voted 68.6% for Proposition 8, which amended the California Constitution to ban same-sex marriages.

The following table includes the number of incidents reported and the rate per 1,000 persons for each type of offense.

[47] Ag production totaled $7.98 billion in 2017, making it the number one agricultural county in the nation.