Prior to the arrival of the Spanish, the area around Rosemead was populated by Amerindians of the Tongva or Gabrielino ethnic group. In 1771, the Spanish founded the first San Gabriel mission in the area that is now known as Whittier Narrows on the border between Montebello and Rosemead. Due to flooding issues, the mission was moved to its present location in San Gabriel in 1775.
During the Spanish colonial period the area now covered by the City of Rosemead was part of the land administered by the San Gabriel Mission. After Mexican independence, the land was distributed to private citizens as part of the Mexican governments secularization act of 1834. The southern part of Rosemead was part of a ranch named Potrero Grande (Large Pasture) which was originally granted to an Amerindian man named Manuel Antonio, who was a "mayordomo" (overseer) at the San Gabriel Mission. The 4,431 acre (18 km²) ranch was later transferred to Juan Matias Sánchez.
Following the Mexican-American War and the signing of the Treaty of Guadalupe which transferred sovereignty over the territory now known as the State of California to the United States, Anglo-American immigration began to flow to the area. In 1852, John Guess and his wife Harriet moved into the San Gabriel Valley from Conway County, Arkansas. In 1855 the couple camped where present-day Savannah Elemetary School is located on Rio Hondo Avenue. They rented land afterwards as the years passed. In 1867, John Guess purchased 100 acres (0.4 km²) of a 1,164 acre (5 km²) ranch and named it Savanna. The land stretched from Valley Boulevard to Marshall Street, and from Rosemead Boulevard to the Eaton Wash.
Other pioneers, Frank Forst and Leonard J. Rose, also settled in this valley. Rose and his wife Amanda bought about 600 acres (2.4 km²) of land between Rosemead Boulevard and Walnut Grove. Rose bred and trained horses for a living. He later named his ranch "Rosemeade." Rosemeade was then renamed Rosemead which flourished with various rabbit and chicken farms.
Rosemead is a working-class suburb with a large population of Latinos and Asians, and the city is sandwiched between Latino-dominated El Monte, California to the east and Asian-populated Monterey Park, California to the west. The Asian influence is particularly felt around the city as many businesses - ranging from restaurants, markets, beauty salons, and auto repair shops - operate in the area: on Garvey Avenue (including the highly popular Diamond Square shopping center anchored by 99 Ranch Market) and to the north near the civic center on Valley Boulevard. Ethnic Chinese are especially represented in the Asian population as many immigrants living in the area are Mainland Chinese and ethnic Chinese from Vietnam. There is also a growing population of ethnic Vietnamese.
Aging trailer parks still remain on Garvey Avenue.
Controversies over the development of a Wal-Mart Supercenter in the southern portion of the city have been ongoing. It recently opened on September 13, 2006. A recall election to remove two councilmembers that supported the Wal-Mart was set for September 19, 2006; the voters defeated the recall in a 60 to 40 percent vote. However, in the general elections that followed shortly thereafter on March 6, 2007, Polly Low defeated incumbent and former recall target Jay Imperial, garnering the highest vote count among the five candidates vying for the two open seats on the council.
The electric giant Edison International is based in the city. Southern California Edison also serves the city. The Chinese cuisine fast food chain Panda Express is headquartered in Rosemead. The Chinese-Vietnamese Sriracha red chili sauce (known to many as Rooster sauce) manufacturer Huy Fong Foods, Inc. (匯豐食品公司) is also based in the city. The University of the West (formerly known as Hsi Lai University) moved to it current location in Rosemead in 1996. It is one of the very first Buddhists funded university in the U.S. Rosemead School of Psychology was named after it's original location in Rosemead. This school was the first independent professional school of psychology in the nation to be accredited by regional accrediting association. Rosemead School of Psychology is now located in La Mirada, but still keeps the city name.
As of the censusGR2 of 2000, there were 53,505 people, 13,913 households, and 11,632 families residing in the city. The population density was 4,011.3/km² (10,398.3/mi²). There were 14,345 housing units at an average density of 1,075.5/km² (2,787.8/mi²). The racial makeup of the city was 26.57% White, 0.68% African American, 0.85% Native American, 48.76% Asian, 0.06% Pacific Islander, 19.69% from other races, and 3.38% from two or more races. Hispanic or Latino of any race were 41.30% of the population.
There were 13,913 households out of which 43.6% had children under the age of 18 living with them, 58.0% were married couples living together, 17.4% had a female householder with no husband present, and 16.4% were non-families. 12.6% of all households were made up of individuals and 5.3% had someone living alone who was 65 years of age or older. The average household size was 3.80 and the average family size was 4.11.
In the city the population was spread out with 27.5% under the age of 18, 10.5% from 18 to 24, 31.7% from 25 to 44, 19.7% from 45 to 64, and 10.6% who were 65 years of age or older. The median age was 32 years. For every 100 females there were 96.4 males. For every 100 females age 18 and over, there were 93.2 males.
The median income for a household in the city was $36,181, and the median income for a family was $36,552. Males had a median income of $26,545 versus $22,353 for females. The per capita income for the city was $12,146. About 19.4% of families and 22.8% of the population were below the poverty line, including 30.6% of those under age 18 and 12.5% of those age 65 or over.
The local homeless population tend to live along the Alhambra wash, and near the San Bernardino Freeway. Day laborers congregate near Garvey Avenue and San Gabriel Boulevard.