In 2005, the population of the city proper was estimated to be over 1.4 million, while the Greater Philadelphia metropolitan area's population of 5.8 million made it the country's fifth-largest. The city is the nation's fourth-largest urban area by population and its fourth-largest consumer media market as ranked by the Nielsen Media Research. It is the county seat of Philadelphia County (with which it is coterminous). Popular nicknames for Philadelphia include Philly and The City of Brotherly Love (from Greek: Φιλαδέλφεια, [pʰi.la.ˈdel.pʰeː.a], Modern Greek: [fi.la'ðɛl.fi.a], "brotherly love" from philos-φίλος, "love", and adelphos-αδερφός or αδελφός "brother").
A commercial, educational, and cultural center, the city was once the second-largest in the British Empire (after London), and the social and geographical center of the original 13 American colonies. Ben Franklin took a large role in Philadelphia's early rise to prominence. It was in this city that many of the ideas, and subsequent actions, gave birth to the American Revolution and American Independence, making Philadelphia a centerpiece of early American history. It was the most populous city of the young United States, and served as the nation's first capital during much of the Revolutionary War and after. Following the ratification of the U.S. Constitution, it was the temporary national capital from 1790 to 1800 while Washington, DC was under construction.
At the 2007 U.S. Census estimates, the city's population was 43.9% White (39.4% non-Hispanic-White alone), 44.9% Black or African American (43.0% non-Hispanic Black or African American alone), 0.7% American Indian and Alaska Native, 5.7% Asian, 0.1% Native Hawaiian and Other Pacific Islander, 6.7% from other races and 1.6% from two or more races. 10.3% of the total population were Hispanic or Latino, most of which are from Puerto Rico.
As of the census of 2000, there were 1,517,550 people, 590,071 households, and 352,272 families residing in the city. The population density was 11,233.6/square mile (4,337.3/km²). There were 661,958 housing units at an average density of 4,900.1/sq mi (1,891.9/km²). As of the 2004 Census estimations, there were 1,463,281 people, 658,799 housing units, and the racial makeup of the city was 45.0% White, 43.2% African American, 5.5% Asian, 0.3% Native American, 0.1% Pacific Islander, 5.8% from other races, and 2.2% from two or more races. Hispanic or Latino of any race were 8.5% of the population. The top 5 largest ancestries include Irish (13.6%), Italian (9.2%), German (8.1%), Polish (4.3%), and English (2.9%).
Of the 590,071 households, 27.6% have children under the age of 18 living with them, 32.1% were married couples living together, 22.3% had a female householder with no husband present, and 40.3% were non-families. 33.8% of all households were made up of individuals and 11.9% had someone living alone who was 65 years of age or older. The average household size was 2.48 and the average family size was 3.22.
In the city the population was spread out with 25.3% under the age of 18, 11.1% from 18 to 24, 29.3% from 25 to 44, 20.3% from 45 to 64, and 14.1% who were 65 years of age or older. The median age was 34 years. For every 100 females there were 86.8 males. For every 100 females age 18 and over, there were 81.8 males.
The median income for a household in the city was $30,746, and the median income for a family was $37,036. Males had a median income of $34,199 versus $28,477 for females. The per capita income for the city was $16,509. About 18.4% of families and 22.9% of the population were below the poverty line, including 31.3% of those under age 18 and 16.9% of those age 65 or over.
As of 2008 more than 500,000 immigrants call the Philadelphia metropolitan area home. More than one-fifth of these immigrants have arrived since 2000, resulting in an increase of 113,000 immigrants between the years 2000 and 2006. This is nearly the same amount of immigrants that arrived during the decade of the 1990s, of which today comprise of 9% of the city's population. As reported by the Brookings Institution, the Philadelphia area is poised to re-emerge as a destination for immigrants, a longtime characteristic of the region that stalled in the mid-20th century.
Philadelphia has the second largest Irish, Italian, and Jamaican populations and the fourth largest African American population in the nation. Philadelphia also has the fourth largest population of Polish residents. In recent years, the Hispanic and Asian American populations have significantly increased. Hispanics have settled throughout the city, especially around El Centro de Oro. Philadelphia is home to the third largest Puerto Rican population in the United States. In recent years many Mexican immigrants have come to areas around the Italian Market. There are an estimated 10,000 Mexicans living in South Philadelphia. Mexicans and Guatemalans also have settled in small communities in North Philadelphia, mainly in the Kensington neighborhood. Colombian immigrants have also come to the Olney neighborhood. The Asian population was once concentrated in the city's thriving Chinatown, but now Korean Americans have come to Olney, and Vietnamese have forged bazaars next to the Italian Market in South Philadelphia. Concentrations of Cambodian American neighborhoods can be found in North and South Philadelphia. Indians and Arabs have come to Northeast Philadelphia along with Russian and Ukrainian immigrants. This large influx of Asians has given Philadelphia one of the largest populations of Vietnamese, Cambodians, Chinese, Indonesians and Koreans in United States. The Philadelphia region also has the fourth largest population of Indian Americans. The West Indian population is concentrated in Cedar Park. Germans, Greeks, Chinese, Japanese, English, Pakistanis, Iranians, and also immigrants from the former Yugoslavia along with other ethnic groups can be found throughout the city.