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 as part of the Program for Action. The complex reasons for these delays are why the line is sometimes called "the line that time forgot".
Work on the line started in 2007 following the development of a financially secure construction plan. The Metropolitan Transportation Authority (MTA) awarded a tunneling contract for the first phase of the project to the consortium of Schiavone/Shea/Skanska (S3) on March 20, 2007. This followed preliminary engineering and a final tunnel design completed by a joint venture between AECOM and Arup. Parsons Brinckerhoff served as the Construction Manager of the project. A full funding grant agreement with the Federal Transit Administration for the first phase of the project was received in November 2007. A ceremonial ground-breaking for the Second Avenue Subway was held on April 12, 2007. The first phase of the line, consisting of three newly built stations and two miles (3.2 km) of tunnel, cost $4.45 billion. A 1.5-mile (2.4 km), $6 billion second phase is in development.