1930 Sumner Tunnel opens, connecting downtown Boston and East Boston.

1957 Massachusetts Turnpike opens from Weston to NY state line.

1959 Elevated Central Artery is finished.

1961 Callahan Tunnel opens under Boston Harbor.

1965 Pike extension opens.

1968 Massachusetts Turnpike Authority proposes a six-lane third harbor tunnel.

1972 Governor Sargent cancels highways planned for Greater Boston except for two projects: a two-lane, Boston Harbor tunnel and study of a new idea — depressing the Central Artery.

1974 Sargent is defeated in the polls by Michael Dukakis who appoints Frederick Salvucci, the artery depression’s most ardent champion, to be state secretary of
transportation.

1978 Edward King defeats Dukakis. He reinvigorates plans for the six-lane tunnel surfacing in East Boston and stops planning for the depressed Central Artery.

1982 Dukakis defeats King and reappoints Salvucci who proposes depressing the Central Artery and building a four-lane, general purpose Boston Harbor Tunnel.

1987 Congress approves a highway and transit bill that commits the federal government to paying 85 percent of the project’s cost, then estimated to be $3.2 billion.

1991 Congress provides additional aid for the project, which is now estimated to cost $5.2 billion.

1992 Construction begins on the Third Harbor Tunnel.

1995 The tunnel, which is named after former Boston Red Sox star Ted Williams, opens, but only to taxis, buses, and trucks.

1998 Though the project’s estimated cost had risen to over $10 billion, including inflation, Congress declines to provide additional funds for its construction.

2000 James Kerasiotes, chair of the Massachusetts Turnpike Authority, which oversees the project, resigns in the wake of revelations that he had concealed a multibillion cost overrun on the project.

2003 The project, now estimated to cost $14.6 billion, opens new roadways in South Boston that connect the turnpike with the Ted Williams Tunnel, which is open to all vehicles. A few months later, the project opens the northbound portion of the depressed artery and new Charles River bridge.