The Boston Subway, also known as the T, is a rapid transit system serving the city of Boston and its surrounding areas. It is the oldest subway system in the United States, having opened in 1897. The system consists of four main lines: the Red Line, Orange Line, Blue Line, and Green Line, which connect various neighborhoods and suburbs. The T operates under the Massachusetts Bay Transportation Authority (MBTA) and provides an essential mode of transportation for residents and visitors. With over 400,000 daily riders, it plays a crucial role in reducing traffic congestion and promoting public transit use in the Greater Boston area.