The Bronx is New York City's northernmost borough. It is the only one of the city's five boroughs situated primarily on the United States mainland rather than on an island. As of 2005, the United States Census Bureau estimated that the borough's population was 1,357,589.[1] Its population has increased since a decline that began after the 1960 census. The borough had its peak population in 1950. [2] The Bronx is the fourth most populous of New York City's five boroughs, and Bronx County is the fifth most populous county in the New York Metropolitan Area.