Preceded by thousands of years of varying cultures, the Caddo people inhabited the Dallas area before Spanish colonists claimed the territory of Texas in the 18th century as a part of the Viceroyalty of New Spain. Later, France also claimed the area but never established much settlement. In all, six flags have flown over the area preceding and during the city's history: those of France, Spain, and Mexico, the flag of the Republic of Texas, the Confederate flag, and the flag of the United States of America.

In 1819, the Adams-Onís Treaty between the United States and Spain defined the Red River as the northern boundary of New Spain, officially placing the future location of Dallas well within Spanish territory.^{[page needed]} The area remained under Spanish rule until 1821, when Mexico declared independence from Spain, and the area was considered part of the Mexican state of Coahuila y Tejas. In 1836, Texians, with a majority of Anglo-American settlers, gained independence from Mexico and formed the Republic of Texas.

Three years after Texas achieved independence, John Neely Bryan surveyed the area around present-day Dallas. In 1839, accompanied by his dog and a Cherokee he called Ned, he planted a stake in the ground on a bluff located near three forks of the Trinity River and left. Two years later, in 1841, he returned to establish a permanent settlement named Dallas. The origin of the name is uncertain. The official historical marker states it was named after Vice President George M. Dallas of Philadelphia, Pennsylvania. However, this is disputed. Other potential theories for the origin include his brother, Commodore Alexander James Dallas, as well as brothers Walter R. Dallas or James R. Dallas. A further theory gives the ultimate origin as the village of Dallas, Moray, Scotland, similar to the way Houston, Texas, was named after Sam Houston whose ancestors came from the Scottish village of Houston, Renfrewshire. The Republic of Texas was annexed by the United States in 1845 and Dallas County was established the following year. Dallas was formally incorporated as a city on February 2, 1856. In the mid-1800s, a group of French Socialists established La Réunion, a short-lived community, along the Trinity River in what is now West Dallas.

With the construction of railroads, Dallas became a business and trading center and was booming by the end of the 19th century. It became an industrial city, attracting workers from Texas, the South, and the Midwest. The Praetorian Building in Dallas of 15 stories, built in 1909, was the first skyscraper west of the Mississippi and the tallest building in Texas for some time. It marked the prominence of Dallas as a city. A racetrack for thoroughbreds was built and their owners established the Dallas Jockey Club. Trotters raced at a track in Fort Worth, where a similar drivers club was based. The rapid expansion of population increased competition for jobs and housing.

In 1921, the Mexican president Álvaro Obregón along with the former revolutionary general visited Downtown Dallas's Mexican Park in Little Mexico; the small park was on the corner of Akard and Caruth Street, site of the current Fairmont Hotel. The small neighborhood of Little Mexico was home to a Latin American population that had been drawn to Dallas by factors including the American Dream, better living conditions, and the Mexican Revolution.

During World War II, Dallas was a major manufacturing center for military automobiles and aircraft for the United States and Allied forces. Over 94,000 jeeps and over 6,000 military trucks were produced at the Ford plant in East Dallas. North American Aviation manufactured over 18,000 aircraft at their plant in Dallas, including the T-6 Texan trainer, P-51 Mustang fighter, and B-24 Liberator bomber.

On November 22, 1963, United States President John F. Kennedy was assassinated on Elm Street while his motorcade passed through Dealey Plaza in Downtown Dallas. The upper two floors of the building from which assassin Lee Harvey Oswald shot Kennedy, the Texas School Book Depository, have been converted into a historical museum covering the former president's life and accomplishments. Kennedy died at Parkland Memorial Hospital, 30 minutes after the shooting.

On July 7, 2016, multiple shots were fired at a Black Lives Matter protest in Downtown Dallas, held against the police killings of two black men from other states. The gunman, later identified as Micah Xavier Johnson, began firing at police officers at 8:58 p.m., killing five officers and injuring nine. Two bystanders were also injured. This marked the deadliest day for U.S. law enforcement since the September 11 attacks. Johnson told police during a standoff that he was upset about recent police shootings of black men and wanted to kill whites, especially white officers. After hours of negotiation failed, police resorted to a robot-delivered bomb, killing Johnson inside El Centro College. The shooting occurred in an area of hotels, restaurants, businesses, and residential apartments only a few blocks away from Dealey Plaza.

Dallas is the ninth most-populous city in the United States and third in Texas after the cities of Houston and San Antonio. Its metropolitan area encompasses one-quarter of the population of Texas, and is the largest in the Southern U.S. and Texas followed by the Greater Houston metropolitan area. In July 2018, the population estimate of the city of Dallas was 1,345,076, an increase of 147,260 since the 2010 United States census.

There were 521,198 households at the 2018 estimates, up from 2010's 458,057 households, out of which 137,758 had children under the age of 18 living with them. 36.6% of households were headed by married couples living together, 14.6% had a female householder with no husband present, and 43.9% were classified as non-family households. In 2010, 33.7% of all households had one or more people under 18 years of age, and 17.6% had one or more people who were 65 years of age or older. The average household size in 2018 was 2.55 and the average family size was 3.48. In 2018 the owner-occupied housing rate was 40.2% and the renter-occupied housing rate was 59.8%. At the 2010 census, the city's age distribution of the population showed 26.5% under the age of 18 and 8.8% who were 65 years of age or older. The median age was 31.8 years. In 2010, 50.0% of the population was male and 50.0% was female. In 2018, the median age 33.3 years. For every 100 females, there were 99.2 males.

According to the 2018 American Community Survey, the median income for a household in the city was $52,210. In 2003-2007's survey, male full-time workers had a median income of $32,265 versus $32,402 for female full-time workers. The per capita income for the city was $25,904. About 18.7% of families and 21.7% of the population were below the poverty line, including 33.6% of those under age 18 and 13.4% of those aged 65 or over. Per 2007's survey, the median price for a house was $129,600.

Dallas's population was historically predominantly white (non-Hispanic whites made up 82.8% of the population in 1930), but its population has diversified due to immigration and white flight over the 20th century. Today the non-Hispanic white population has declined to less than one-third of the city's population.

According to the 2010 census, 50.7% of the population was White (28.8% non-Hispanic white), 24.8% was Black or African American, 0.7% American Indian and Alaska Native, 2.9% Asian, and 2.6% from two or more races. 42.4% of the total population was of Hispanic or Latino origin (they may be of any race). In the United States Census Bureau's 2018 estimates, 29.3% were non-Hispanic white, 24.8% Black or African American, 0.2% American Indian or Alaska Native, 3.4% Asian, and 1.5% from two or more races.Native Hawaiian and other Pacific Islanders made up a total of 606 residents according to 2017's estimates. Hispanics or Latinos of any race made up 40.7% of the estimated population in 2018. Among the Hispanic or Latin American population in 2018, 34.0% of Dallas was Mexican, 0.4% Puerto Rican, 0.2% Cuban and 5.9% other Hispanic or Latino. In 2017's American Community Survey estimates among the demographic 35.5% were Mexican, 0.6% Puerto Rican, 0.4% Cuban, and 5.4% other Hispanic or Latino.

The Dallas area is a major destination for Mexican Americans and Hispanic immigrants. The southwestern portion of the city, particularly Oak Cliff is chiefly inhabited by Hispanic and Latin American residents. The southeastern portion of the city Pleasant Grove is chiefly inhabited by African American and Hispanic or Latino residents, while the southern portion of the city is predominantly black. The west and east sides of the city are predominantly Hispanic or Latino; Garland also has a large Spanish speaking population. North Dallas has many enclaves of predominantly white, black and especially Hispanic or Latino residents.

The Dallas area is also a major destination for African Americans. Between 2000 and 2010, the Dallas area gained 223,000 new African American residents only behind the Atlanta metropolitan area. The notable influx of African Americans is partly due to the New Great Migration. There is a significant number of people from the Horn of Africa, immigrants from Ethiopia, Eritrea and Somalia.

The Dallas–Fort-Worth metroplex had an estimated 70,000 Russian-speakers (as of November 6, 2012) mostly immigrants from the former Soviet Bloc. Included in this population are Russians, Russian Jews, Ukrainians, Belarusians, Moldavians, Uzbek, Kirghiz, and others. The Russian-speaking population of Dallas has continued to grow in the sector of "American husbands-Russian wives". Russian DFW has its own newspaper, The Dallas Telegraph.

In addition, Dallas and its suburbs are home to a large number of Asian Americans including those of Indian, Vietnamese, Chinese, Korean, Filipino, Japanese, and other heritage. Among large-sized cities in the United States, Plano, the northern suburb of Dallas, has the 6th largest Chinese American population as of 2016. The Plano-Richardson area in particular had an estimated 30,000 Iranian Americans in 2012. With so many immigrant groups, there are often multilingual signs in the linguistic landscape. According to U.S. Census Bureau data released in December 2013, 23 percent of Dallas County residents were foreign-born, while 16 percent of Tarrant County residents were foreign-born. The 2018 census estimates determined that the city of Dallas's foreign-born population consisted of 25.4% naturalized citizens and 74.6% non-citizens.

Recognized for having one of the largest lesbian, gay, bisexual, and transgender (LGBT) populations in the nation, Dallas and the Metroplex are widely noted for being home to a vibrant and diverse LGBT community. Throughout the year there are many well-established LGBT events held in the area, most notably the annual Alan Ross Texas Freedom (Pride) Parade and Festival in June which draws approximately 50,000. For decades, the Oak Lawn and Bishop Arts districts have been known as the epicenters of LGBT culture in Dallas.

Christianity is the most prevalently practiced religion in Dallas and the wider metropolitan area according to a 2014 study by the Pew Research Center (78%). There is a large Protestant Christian influence in the Dallas community, though the city of Dallas and Dallas County have more Catholic than Protestant residents, while the converse is usually true for the suburban areas of Dallas and the city of Fort Worth.

Dallas has been called the "Prison Ministry Capital of the World" by the prison ministry community. It is a home for the International Network of Prison Ministries, the Coalition of Prison Evangelists, Bill Glass Champions for Life, Chaplain Ray's International Prison Ministry, and 60 other prison ministries.

Methodist, Baptist, and Presbyterian churches are prominent in many neighborhoods and anchor two of the city's major private universities (Southern Methodist University and Dallas Baptist University). Dallas is also home to two evangelical seminaries: the Dallas Theological Seminary and Criswell College. Many Bible schools including Christ For The Nations Institute are also headquartered in the city. The Christian creationist apologetics group Institute for Creation Research is headquartered in Dallas. According to the Pew Research Center, Evangelical Protestantism constituted the largest form of Protestantism in the area as of 2014. The largest single Evangelical Protestant group were Baptists. The largest Baptist denomination was the Southern Baptist Convention, followed by the historically black National Baptist Convention USA.African-initiated Protestant churches including Ethiopian Evangelical churches can be found throughout the metropolitan area.

The Catholic Church is also a significant religious organization in the Dallas area and operates the University of Dallas, a liberal-arts university in the Dallas suburb of Irving. The Cathedral Santuario de la Virgen de Guadalupe in the Arts District is home to the second-largest Catholic church membership in the United States and overseas, consisting over 70 parishes in the Dallas Diocese. The Society of Jesus operates the Jesuit College Preparatory School of Dallas. Dallas is also home to numerous Eastern Orthodox and Oriental Orthodox churches including Saint Seraphim Cathedral, see of the Orthodox Church in America's Southern Diocese. The Greek Orthodox Archdiocese of America (Ecumenical Patriarchate) has one parish in the city of Dallas.

The city is home to a sizable Latter Day Saint community. The Church of Jesus Christ of Latter-day Saints has twenty-three stakes throughout Dallas and surrounding suburbs. The organization built the Dallas Texas Temple, the first temple in Texas, in the city in 1984.Jehovah's Witnesses also have a large number of members throughout the Dallas metropolitan division. In addition, there are several Unitarian Universalist congregations, including First Unitarian Church of Dallas, founded in 1899. A large community of the United Church of Christ exists in the city. The most prominent UCC-affiliated church is the Cathedral of Hope, a predominantly LGBT-affirming church.

Dallas's Jewish population of approximately 45,000 is one of the largest of any city in Texas. Since the establishment of the city's first Jewish cemetery in 1854 and its first congregation (which would eventually be known as Temple Emanu-El) in 1873, Dallasite Jews have been well represented among leaders in commerce, politics, and various professional fields in Dallas and elsewhere. Furthermore, a large Muslim community exists in the north and northeastern portions of Dallas, as well as in the northern Dallas suburbs. The oldest mosque in Dallas is Masjid Al-Islam just south of Downtown.

Dallas has a large Buddhist community. Immigrants from East Asia, Southeast Asia, Nepal, and Sri Lanka have all contributed to the Buddhist population, which is concentrated in the northern suburbs of Garland, Plano and Richardson. Numerous Buddhist temples dot the Metroplex including The Buddhist Center of Dallas, Lien Hoa Vietnamese Temple of Irving, and Kadampa Meditation Center Texas and Wat Buddhamahamunee of Arlington. A large and growing Hindu Community lives in the Dallas–Fort Worth metroplex. Most live in Collin County and the northern portions of Dallas County. Over 28 Hindu Temples exist in the area. Some notable ones include North Texas Hindu Mandir, Radha Krishna Temple, Dallas and Karya Siddhi Hanuman Temple. There are also at least three Sikh Gurudwaras in this metropolitan area. For irreligious people, the Winter Solstice Celebration is held in the Metroplex although some of its participants are also neo-pagans and New Agers.

According to the FBI, a city to city comparison of crime rates can be misleading, because recording practices vary from city to city, citizens report different percentages of crimes from one city to the next, and the actual number of people physically present in a city is unknown. With that in mind, Dallas's violent crime rate (12.06 per 1,000 people) is lower than St Louis (24.81), Detroit (24.22), Baltimore (16.96), Philadelphia (15.62), Cleveland (15.47), Miami (15.09), Washington, D.C. (14.48), Kansas City (14.44) and Boston (13.39). However, Houston (11.69), Los Angeles (7.87), and New York City (6.38) have lower violent crime rates than Dallas.