Lower Manhattan, also known as Downtown Manhattan or Downtown New York City, is the southernmost part of Manhattan, the central borough of New York City. The neighborhood is the historical birthplace of New York City and for its first 225 years was the entirety of the city. Lower Manhattan serves as the seat of government of both Manhattan and the entire City of New York. Because there are no municipally defined boundaries for the neighborhood, a precise population cannot be quoted, but several sources have suggested that it was one of the fastest-growing locations in New York City between 2010 and 2020, related to the influx of young adults and significant development of new housing units.