The Bronx has a land area of 42 square miles (109 km2) and a population of 1,471,160 in 2017. Of the five boroughs, it has the fourth-largest area, fourth-highest population, and third-highest population density. It is the only borough predominantly on the U.S. mainland.
The Bronx is divided by the Bronx River into a hillier section in the west, and a flatter eastern section. East and west street names are divided by Jerome Avenue—the continuation of Manhattan's Fifth Avenue. The West Bronx was annexed to New York City in 1874, and the areas east of the Bronx River in 1895. Bronx County was separated from New York County in 1914. About a quarter of the Bronx's area is open space, including Woodlawn Cemetery, Van Cortlandt Park, Pelham Bay Park, the New York Botanical Garden, and the Bronx Zoo in the borough's north and center. These open spaces are situated primarily on land deliberately reserved in the late 19th century as urban development progressed north and east from Manhattan.
The name "Bronx" originated with Jonas Bronck, who established the first settlement in the area as part of the New Netherland colony in 1639. The native Lenape were displaced after 1643 by settlers. In the 19th and 20th centuries, the Bronx received many immigrant and migrant groups as it was transformed into an urban community, first from various European countries (particularly Ireland, Germany, and Italy) and later from the Caribbean region (particularly Puerto Rico, Haiti, Jamaica, and the Dominican Republic), as well as African American migrants from the southern United States. This cultural mix has made the Bronx a wellspring of Latin music hip hop and rock.
The Bronx contains one of the five poorest Congressional Districts in the United States, the 15th, but its wide diversity also includes affluent, upper-income and middle-income neighborhoods such as Riverdale, Fieldston, Spuyten Duyvil, Schuylerville, Pelham Bay, Pelham Gardens, Morris Park, and Country Club. The Bronx, particularly the South Bronx, saw a sharp decline in population, livable housing, and the quality of life in the late 1960s and the 1970s, culminating in a wave of arson. Since then the communities have shown significant redevelopment starting in the late 1980s before picking up pace from the 1990s until today.
The Bronx was called Rananchqua by the native Siwanoy band of Lenape (also known historically as the Delawares), while other Native Americans knew the Bronx as Keskeskeck. It was divided by the Aquahung River.
The origin of the person of Jonas Bronck (c. 1600–43) is contested. Some sources claim he was a Swedish born emigrant from Komstad, Norra Ljunga parish in Småland, Sweden, who arrived in New Netherland during the spring of 1639. Bronck became the first recorded European settler in the area now known as the Bronx and built a farm named "Emmanus" close to what today is the corner of Willis Avenue and 132nd Street in Mott Haven. He leased land from the Dutch West India Company on the neck of the mainland immediately north of the Dutch settlement in Harlem (on Manhattan Island), and bought additional tracts from the local tribes. He eventually accumulated 500 acres (200 ha) between the Harlem River and the Aquahung, which became known as Bronck's River or the Bronx . Dutch and English settlers referred to the area as Bronck's Land. The American poet William Bronk was a descendant of Pieter Bronck, either Jonas Bronck's son or his younger brother. More recent research indicates that Pieter was probably Jonas' nephew or cousin, but certainly of the same family.
The Bronx is referred to with the definite article as "The Bronx", both legally and colloquially. The County of Bronx does not place "The" immediately before "Bronx" in formal references, unlike the coextensive Borough of the Bronx, nor does the United States Postal Service in its database of Bronx addresses (the city and state mailing-address format is simply "Bronx, NY"). The region was apparently named after the Bronx River and first appeared in the "Annexed District of The Bronx" created in 1874 out of part of Westchester County. It was continued in the "Borough of The Bronx", which included a larger annexation from Westchester County in 1898. The use of the definite article is attributed to the style of referring to rivers. Another explanation for the use of the definite article in the borough's name is that the original form of the name was a possessive or collective one referring to the family, as in visiting "the Broncks", "the Bronck's", or "the Broncks'".