Queens is a borough of New York City, coterminous with Queens County, in the U.S. state of New York. It is the largest borough geographically and is adjacent to the borough of Brooklyn. To its east is Nassau County. Queens also shares water borders with the boroughs of Manhattan and the Bronx. The borough of Queens is the second-largest in population, the first being Brooklyn; with an estimated population of 2,278,906 residents in 2018, approximately 47.5 percent of them foreign-born. Queens County also is the second most populous county in the U.S. state of New York, behind Brooklyn, which is coterminous with Kings County. Queens is the fourth most densely populated county among New York City's boroughs, as well as in the United States. If each of New York City's boroughs were an independent city, Queens would be the nation's fourth most populous, after Los Angeles, Chicago, and Brooklyn. Queens is one of the most ethnically diverse counties in the United States, as well as the most diverse among highly populated counties From 1683 until 1899, the County of Queens included what is now Nassau County. Queens became a borough during the consolidation of New York City in 1898. Queens has the most diversified economy of the five boroughs of New York City. It is home to John F. Kennedy International Airport and LaGuardia Airport, both among the world's busiest, which in turn makes the airspace above Queens among the busiest in the United States. Landmarks in Queens include Flushing Meadows–Corona Park; Citi Field, home to the New York Mets baseball team; the USTA Billie Jean King National Tennis Center, site of the US Open tennis tournament; Kaufman Astoria Studios; Silvercup Studios; and Aqueduct Racetrack. The borough has diverse housing, ranging from high-rise apartment buildings in the urban areas of western and central Queens, such as Ozone Park, Jackson Heights, Flushing, Astoria, and Long Island City, to somewhat more suburban neighborhoods in the eastern part of the borough, including Douglaston–Little Neck and Bayside. The Queens Night Market in Flushing Meadows-Corona Park attracts over 10,000 people nightly to sample food from over 85 countries.