Staten Island's lack of a subway system can be attributed to a complex interplay of historical, geographical, and logistical factors. Unlike other boroughs of New York City, Staten Island's separation by waterways, primarily the Upper New York Bay, creates a significant geographical barrier. The island's population density and development patterns historically differed from the rest of the city, leading to less immediate demand for a subway system. Additionally, the construction of a subway line would involve substantial costs, logistical challenges related to tunneling beneath waterways, and potential disruption to existing infrastructure. Instead, Staten Island primarily relies on an extensive network of buses, ferries, and railways connecting it to the rest of New York City.