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 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 origin of the person of Jonas Bronck (c. 1600–43) has been contested. Documents indicate that 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 "Emmaus" 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 of New Haarlem (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 [River]. 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, but most probably a nephew or cousin, as there was an age difference of 16 years. Much work on the Swedish claim has been undertaken by Brian G. Andersson former Commissioner of NYC's Dept. of Records, who assisted in organizing a 375th Anniversary celebration in Bronck's hometown in 2014. 
Use of definite article
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. A time-worn story explanation for the use of the definite article in the borough's name stems from the phrase "visiting the Broncks", referring to the settler's family.
The capitalization of the borough's name is sometimes disputed. Generally, the definite article is lowercase in place names ("the Bronx") except in official references. The definite article is capitalized ("The Bronx") at the beginning of a sentence or in any other situation when a normally lowercase word would be capitalized. However, some people and groups refer to the borough with a capital letter at all times, such as Lloyd Ultan, a historian for The Bronx County Historical Society, and the Great and Glorious Grand Army of The Bronx, a Bronx-based organization. These people say that the definite article is part of the proper name. In particular, the Great and Glorious Grand Army of The Bronx is leading efforts to make the city refer to the borough with an uppercase definite article in all uses, comparing the lowercase article in the Bronx's name to "not capitalizing the 's' in 'Staten Island.'"