The Bronx is one of the five boroughs of New York City, in the U.S. state of New York. It has the same boundaries as Bronx County, the third-most-densely populated county in the United States. The Bronx is south of Westchester County; northeast and east of the New York City borough of Manhattan, across the Harlem River; and north of the New York City borough of Queens, across the East River. The Bronx has a land area of 42 square miles (109 km2) and a population of 1,418,207 in 2019. Of the five boroughs, it has the fourth-largest area, fourth-highest population, and third-highest population density. It is the only borough of New York City predominantly on the mainland.