The IRT East Side Line is a rapid transit line in New York City, part of the New York City Subway. It primarily serves the east side of Manhattan, running from City Hall in the south to East 180th Street in the Bronx. The line is known for its numbered routes, including the 4, 5, and 6 trains. Opened in 1904, the IRT East Side Line was one of the first subway lines in the city. It has undergone various upgrades and expansions over the years, enhancing its capacity and service reliability. The line plays a crucial role in connecting neighborhoods and facilitating daily commutes for thousands of riders.