Lower Manhattan, also known as Downtown Manhattan, is the southernmost part of the New York City borough of Manhattan. The area is the historical birthplace of New York City and in the 17th and 18th centuries composed 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 area. 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.