The 23rd Street Crosstown is a surface transit line on 23rd Street in Manhattan, New York City. It currently hosts the M23 SBS bus route of the Metropolitan Transportation Authority (MTA)'s Regional Bus Operations. The M23 runs between Chelsea Piers, along the West Side Highway near 22nd Street, via 23rd Street, to Avenue C and 20th Street in Stuyvesant Town–Peter Cooper Village. The route was originally the Twenty-third Street Railway, a street railway that was originally operated as horse cars and later electric traction. The company was chartered on January 29, 1872. The Twenty-third Street Railway was leased by numerous larger companies in the late 19th and early 20th century. The trolley line was replaced with bus service in 1936 and was originally numbered the M18-15 and the M26 before gaining the current M23 designation in 1989. On November 6, 2016, it became a Select Bus Service (SBS) route. Route For most of its length, the M23 uses 23rd Street to travel crosstown. There is a one-block stretch of the route, between 11th and 12th Avenues, that runs along 24th Street; this is because the M23 needs to access a bus loop at Chelsea Piers, which is along the West Side Highway near 22nd Street, but it must use 24th Street since 23rd Street ends at 11th Avenue. The westbound route between Avenue C and 1st Avenue runs along 20th Street because its eastern terminal is in the southbound lanes of Avenue C in Stuyvesant Town–Peter Cooper Village. Connections The M23 intersects with every New York City Bus line that it encounters along its crosstown route, as well as some New York City Subway stations. Along Avenue C and 20th Street in Peter Cooper Village, in both directions, the M23 shares bus stops with the M9 route. At the intersections of both 20th and 23rd Streets with 1st Avenue, the northbound M15 and M15 Select Bus Service (SBS) has stops on 1st Avenue, close to the M23 stops. The corresponding southbound M15/M15 SBS stops are at 2nd Avenue. The southbound M9 and eastbound M34A SBS share an eastbound run with the M23 between 2nd Avenue and FDR Drive. At 3rd Avenue, the M101, M102, and M103 are all nearby. The northbound M1, M2, and M3 stop on Park Avenue. The 23rd Street subway station of the IRT Lexington Avenue Line, under Park Avenue, serves the . At 5th Avenue and