Indigenous people have lived in coastal Southern California for over 10,000 years, and several successive cultures have inhabited the present-day area of Long Beach. By the 16th-century arrival of Spanish explorers, the dominant group was the Tongva people. They had at least three major settlements within the present-day city. Tevaaxa'anga was an inland settlement near the Los Angeles River, while Ahwaanga and Povuu'nga were coastal villages. Along with other Tongva villages, they were forced to relocate in the mid-19th century due to missionization, political change, and a drastic drop in population from exposure to European diseases.

In 1784, the Spanish Empire's King Carlos III granted Rancho Los Nietos to Spanish soldier Manuel Nieto. The Rancho Los Cerritos and Rancho Los Alamitos were divided from this territory. The boundary between the two ranchos ran through the center of Signal Hill on a southwest to northeast diagonal. A portion of western Long Beach was originally part of the Rancho San Pedro. Its boundaries were in dispute for years, due to flooding changing the Los Angeles River boundary between Rancho San Pedro and Rancho Los Nietos.

In 1843, Jonathan Temple bought Rancho Los Cerritos, having arrived in California in 1827 from New England. He built what is now known as the "Los Cerritos Ranch House", a still-standing adobe which is a National Historic Landmark. Temple created a thriving cattle ranch and prospered, becoming the wealthiest man in Los Angeles County. Both Temple and his ranch house played important local roles in the Mexican–American War. On an island in the San Pedro Bay, Mormon pioneers made an abortive attempt to establish a colony (as part of Brigham Young's plan to establish a continuous chain of settlements from the Pacific to Salt Lake).

In 1866, Temple sold Rancho Los Cerritos for $20,000 to the Northern California sheep-raising firm of Flint, Bixby & Company, which consisted of brothers Thomas and Benjamin Flint and their cousin Lewellyn Bixby. Two years previous Flint, Bixby & Co had also purchased along with Northern California associate James Irvine, three ranchos which would later become the city that bears Irvine's name. To manage Rancho Los Cerritos, the company selected Lewellyn's brother Jotham Bixby, the "Father of Long Beach". Three years later, Bixby bought into the property and would later form the Bixby Land Company. In the 1870s, as many as 30,000 sheep were kept at the ranch and sheared twice yearly to provide wool for trade. In 1880, Bixby sold 4,000 acres (16 km²) of the Rancho Los Cerritos to William E. Willmore, who subdivided it in hopes of creating a farm community, Willmore City. He failed and was bought out by a Los Angeles syndicate that called itself the "Long Beach Land and Water Company." They changed the name of the community to Long Beach at that time.

The City of Long Beach was officially incorporated in 1897.

The town grew as a seaside resort with light agricultural uses.The Pike was the most famous beachside amusement zone on the West Coast from 1902 until 1969; it offered bathers food, games and rides, such at the Sky Wheel dual Ferris wheel and Cyclone Racer roller coaster. Gradually the oil industry, Navy shipyard and facilities and port became the mainstays of the city. In the 1950s it was referred to as "Iowa by the sea," due to a large influx of people from that and other Midwestern states. Huge picnics for migrants from each state were a popular annual event in Long Beach until the 1960s.

Another Bixby cousin, John W. Bixby, was influential in the city. After first working for his cousins at Los Cerritos, J.W. Bixby leased land at Rancho Los Alamitos. He put together a group: banker I.W. Hellman, Lewellyn and Jotham Bixby, and him, to purchase the rancho. In addition to bringing innovative farming methods to the Alamitos (which under Abel Stearns in the late 1850s and early 1860s was once the largest cattle ranch in the US), J.W. Bixby began the development of the oceanfront property near the city's picturesque bluffs. Under the name Alamitos Land Company, J.W. Bixby named the streets and laid out the parks of his new city. This area would include Belmont Heights, Belmont Shore and Naples; it soon became a thriving community of its own. J.W. Bixby died in 1888 of apparent appendicitis. The Rancho Los Alamitos property was split up, with Hellman getting the southern third, Jotham and Lewellyn, the northern third, and J.W. Bixby's widow and heirs keeping the central third. The Alamitos townsite was kept as a separate entity, but at first, it was primarily run by Lewellyn and Jotham Bixby, although I.W, Hellman (who had the largest single share) had a significant veto power, an influence made even stronger as the J.W. Bixby heirs began to side with Hellman more and more.

When Jotham Bixby died in 1916, the remaining 3,500 acres (14 km²) of Rancho Los Cerritos was subdivided into the neighborhoods of Bixby Knolls, California Heights, Los Cerritos, North Long Beach and part of the city of Signal Hill.

Pine Avenue near 4th became the center of a large shopping district. Besides upscale Buffums (1912; expanded 1926), in 1929 alone Barker Brothers, the Hugh A. Marti Co., and Wise Company department stores built large new stores,Walker's (1933), and nearby at American and 5th, Sears (1928) and Montgomery Ward (1929). It would remain popular until suburban malls sprung up starting in the 1950s. (see also: History of Retail in Southern California)

Oil was discovered in 1921 on Signal Hill, which split off as a separately incorporated city shortly afterward. The discovery of the Long Beach Oil Field, brought in by the gusher at the Alamitos oil well #1, made Long Beach a major oil producer; in the 1920s the field was the most productive in the world. In 1932, the even larger Wilmington Oil Field, fourth-largest in the United States, and which is mostly in Long Beach, was developed, contributing to the city's fame in the 1930s as an oil town.

The M6.4 1933 Long Beach earthquake caused significant damage to the city and surrounding areas, killing a total of 120 people. Most of the damage occurred in unreinforced masonry buildings, especially schools. Pacific Bible Seminary (now known as Hope International University) was forced to move classes out of First Christian Church of Long Beach and into a small local home due to damage.

The Ford Motor Company built a factory called Long Beach Assembly at the then address in 1929 as "700 Henry Ford Avenue, Long Beach" where the factory began building the Ford Model A. Production of Ford vehicles continued after the war until 1960 when the plant was closed due to a fire, and January 1991 when the factory was demolished partially due to air quality remediation efforts. Ford had earlier opened a Factory in Los Angeles at the location of 12th Street and Olive, with a later factory built at East Seventh Street and Santa Fe Avenue after 1914.

Come 1938, the creation of Housing Authorities for both the City and County of Los Angeles were complete — and North Long Beach was to be home to the County Authority's first order of business: the Carmelitos Housing Project, Southern California's first affordable housing complex.

The city was part of the Battle of Los Angeles during World War II when observers for the United States Army Air Forces reported shells being fired from the sea. Anti-aircraft batteries fired into the night sky, although no planes were ever sighted.

Before the war, Long Beach had a sizable Japanese-American population, who worked in the fish canneries on Terminal Island and owned small truck (produce) farms in the area. Due to exaggerated fears on the coast and racial prejudice, state officials persuaded the national government to remove Japanese nationals and Japanese Americans for internment in 1942 to inland facilities. Most did not return to the city after their release from the camps. Due to this and other factors, Japanese Americans now make up less than 1% of the population of Long Beach, but the Japanese Community Center and a Japanese Buddhist Church survive. The Japanese-American Cultural Center is over the Gerald Desmond Bridge and the Vincent Thomas Bridge in San Pedro.

Douglas Aircraft Company's largest facility was its Long Beach plant, totaling 1,422,350 sq. ft. The first plane rolled out the door on December 23, 1941. The plant produced C-47 Skytrain transports, B-17 Flying Fortress bombers, and A-20 Havoc attack bombers simultaneously. Douglas merged with the McDonnell Aircraft Company in 1967 where the Douglas DC-8 and the McDonnell Douglas DC-9 were built. In 1997 McDonnell Douglas merged with Boeing, which made C-17 Globemaster transport planes in Long Beach until the close of the manufacturing facility in 2015.

The 2010 United States Census reported that Long Beach had a population of 462,257. The population density was 9,191.3 people per square mile (3,548.8/km²). The racial makeup of Long Beach was 213,066 (46.1%) White, 62,603 (13.5%) Black or African American, 3,458 (0.7%) Native American, 59,496 (12.9%) Asian (4.5% Filipino, 3.9% Cambodian, 0.9% Vietnamese, 0.6% Chinese, 0.6% Japanese, 0.4% Indian, 0.4% Korean, 0.2% Thai, 0.1% Laotian, 0.1% Hmong), 5,253 (1.1%) Pacific Islander (0.8% Samoan, 0.1% Guamanian, 0.1% Tongan), 93,930 (20.3%) from other races, and 24,451 (5.3%) from two or more races. Hispanic or Latino of any race were 188,412 persons (40.8%). 32.9% of the city's population was of Mexican heritage.Non-Hispanic Whites were 29.4% of the population in 2010, down from 86.2% in 1970.

The ethnic Cambodian population of approximately 20,000 is the largest outside of Asia.

The Census reported 453,980 people (98.2% of the population) lived in households, 5,321 (1.2%) lived in non-institutionalized group quarters, and 2,956 (0.6%) were institutionalized.

There were 163,531 households, out of which 58,073 (35.5%) had children under the age of 18 living in them, 61,850 (37.8%) were opposite-sex married couples living together, 26,781 (16.4%) had a female householder with no husband present, 10,598 (6.5%) had a male householder with no wife present. There were 12,106 (7.4%) unmarried opposite-sex partnerships, and 3,277 (2.0%) same-sex married couples or partnerships. Of the households, 46,536 (28.5%) were made up of individuals, and 11,775 (7.2%) had someone living alone who was 65 years of age or older. The average household size was 2.78. There were 99,229 families (60.7% of all households); the average family size was 3.52.

The age distribution of the city was as follows: 115,143 people (24.9%) were under the age of 18, 54,163 people (11.7%) aged 18 to 24, 140,910 people (30.5%) aged 25 to 44, 109,206 people (23.6%) aged 45 to 64, and 42,835 people (9.3%) who were 65 years of age or older. The median age was 33.2 years. For every 100 females, there were 96.1 males. For every 100 females age 18 and over, there were 93.8 males.

There were 176,032 housing units at an average density of 3,422.2 per square mile (1,321.3/km²), of which 67,949 (41.6%) were owner-occupied, and 95,582 (58.4%) were occupied by renters. The homeowner vacancy rate was 2.0%; the rental vacancy rate was 7.2%. 195,254 people (42.2% of the population) lived in owner-occupied housing units and 258,726 people (56.0%) lived in rental housing units.

During 2009–2013, Long Beach had a median household income of $52,711, with 20.2% of the population living below the federal poverty line.

As of 2014, the population of Long Beach was 473,577.

As of the census of 2000, there were 461,522 people, 163,088 households, and 99,646 families residing in the city. The population density was 9,149.8 inhabitants per square mile (3,532.8/km²). There were 171,632 housing units at an average density of 3,402.6 per square mile (1,313.8/km²). The racial makeup of the city was 45.2% White, 14.9% Black or African American (U.S. Census), 0.8% Native American, 12.1% Asian, 1.2% Pacific Islander, 20.6% from other races, and 5.3% from two or more races. Hispanic or Latino people of any race were 35.8% of the population.

The city has changed since the 1950s, when its population was predominantly European-American and the city was nicknamed "Iowa by the Sea" or "Iowa under Palm Trees" as it had a slower pace than neighboring Los Angeles. In 1950, whites represented 97.4% of Long Beach's population. Since the second half of the 20th century, the city has been a major port of entry for Asian and Latin American immigrants headed to Los Angeles. The Harbor section of downtown Long Beach was once home to people of Dutch, Greek, Italian, Maltese, Portuguese and Spanish ancestry, most of them employed in manufacturing and fish canneries until the 1960s.

According to a report by USA Today in 2000, Long Beach is the most ethnically diverse large city in the United States. Non-Hispanic White Americans made up 30.0% of the city's population. Its Asian community includes the largest Cambodian community in the United States, and the second-largest Cambodian community outside of Asia (after Paris). A neighborhood along Anaheim Street is called "Little Phnom Penh". There are also sizable populations of immigrants and descendants from Vietnam and the Philippines.

Long Beach had offered many industrial jobs to African Americans during the years of World War II. This resulted in the increase of blacks in Long Beach caused by the Second Great Migration. There are black communities in the Eastside, North Long Beach, and Upper Westside neighborhoods.

It has a relatively high proportion of Pacific Islanders (over 1% as of the 2000 Census), from Samoa and Tonga. Most American Indians, about 0.8% of the city's population, arrived during the Department of the Interior's Bureau of Indian Affairs urban relocation programs in the 1950s.

Long Beach once had a sizable Japanese American population, which largely worked in the fish canneries on Terminal Island and on small truck farms in the area. In 1942, not long after the Attack on Pearl Harbor and subsequent Japanese declaration of war on the United States and the British Empire, President Franklin D. Roosevelt issued United States Executive Order 9066 which allowed military commanders to designate areas "from which any or all persons may be excluded." Under this order, all Japanese and Americans of Japanese ancestry were categorically removed from Western coastal regions and sent to internment camps, without regard for due process. Most did not return to Long Beach after their release from the camps. Japanese Americans make up less than 1% of the population of Long Beach, yet the city still has a Japanese Community Center and a Japanese Buddhist Church from its earlier history.

As of the 2000 census, there were 163,088 households, out of which 35.0% had children under the age of 18 living with them, 39.2% were married couples living together, 16.1% had a female householder with no husband present, and 38.9% were non-families. Of all households, 29.6% were made up of individuals, and 7.4% had someone living alone who was 65 years of age or older. The average household size was 2.77 and the average family size was 3.55.

In the city, the population was spread out, with 29.2% under the age of 18, 10.9% from 18 to 24, 32.9% from 25 to 44, 18.0% from 45 to 64, and 9.1% who were 65 years of age or older. The median age was 31 years. For every 100 females, there were 96.6 males. For every 100 females age 18 and over, there were 93.5 males.

The median income for a household in the city was $37,270, and the median income for a family was $40,002. Males had a median income of $36,807 versus $31,975 for females. The per capita income for the city was $19,040. About 19.3% of families and 22.8% of the population were below the poverty line, including 32.7% of those under age 18 and 11.0% of those age 65 or over. In 2008, the Census Bureau showed the number of people living below the poverty line had dropped to 18.2%.