The IRT Flushing Line is a rapid transit route of the New York City Subway system, named for its eastern terminal in Flushing, Queens. It is operated as part of the A Division. The Interborough Rapid Transit Company (IRT), a private operator, had constructed the section of the line from Flushing, Queens, to Times Square, Manhattan between 1915 and 1928. A western extension was opened to Hudson Yards in western Manhattan in 2015, and the line now stretches from Flushing to Chelsea, Manhattan. It carries trains of the local service, as well as the express during rush hours in the peak direction. It is the only currently operational IRT line to serve Queens. It is shown in the color on station signs, the official subway map, and internal route maps in R188 cars. Before the line was opened all the way to Flushing in 1928, it was known as the Corona Line or Woodside and Corona Line. Prior to the discontinuation of BMT services in 1949, the portion of the IRT Flushing Line between Times Square and Queensboro Plaza was known as the Queensboro Line. Since the mid-2010s, the line's signal system has been converted to an automated system. The Flushing Line has various styles of architecture, which range from steel girder elevated structures to European-style concrete viaducts. The underground stations have some unique designs as well. The designs include Hunters Point Avenue, which is in an Italianate style; Grand Central–42nd Street, which is a single round tube similar to a London Underground station; and 34th Street–Hudson Yards, which, with its deep vault and spacious interior, resembles a Washington Metro station. Extent and service Route Services that use the Flushing Line are colored . The following services use part or all of the IRT Flushing Line: The line has two distinct sections, split by the Queensboro Plaza station. It begins as a three-track subway, with the center track used for express service, at Flushing–Main Street. It quickly leaves the ground onto a steel elevated structure above Roosevelt Avenue, passing Citi Field and the United States Tennis Association's National Tennis Center. A flying junction between Mets–Willets Point and 111th Street provides access to the Corona Yard from the local tracks. At 48th Street in Sunnyside, the line switches to Queens Boulevard and an ornate concrete viaduct begins. The express track ends between 33rd Street–Rawson Street and Queensboro Plaza. At Queensboro Plaza,