The Second Avenue Subway, a New York City Subway line that runs under Second Avenue on the East Side of Manhattan, has been proposed since 1920. The first phase of the line, consisting of three stations on the Upper East Side, started construction in 2007 and opened in 2017, ninety-seven years after the route was first proposed. Up until the 1960s, many distinct plans for the Second Avenue subway line were never carried out, though small segments were built in the 1970s. The complex reasons for these delays are why the line is sometimes called "the line that time forgot".