The tunnel, which opened on November 23, 1985, closed a gap in I-95 between Maine and Florida. At the time of its opening it was the most expensive underwater tunnel project in the United States, but that figure has since been surpassed by the Big Dig project in Boston.
The Fort McHenry Tunnel was constructed from June 1980 to November 1985, at a cost of about $750 million. The tunnel's annual traffic in 2009 was 43.4 million vehicles. As of July 1, 2013, the toll rate for cars is $4.00, paid in either direction. Vehicles with more than two axles pay additional amounts, up to $30.00 for six axles.
The Fort McHenry Tunnel was opened on time and under its budget, and it continues to be a vital transportation link in the Mid-Atlantic region. Soon after the Fort McHenry Tunnel opened, the nearby Baltimore Harbor Tunnel, which had opened to traffic in 1957, was extensively rehabilitated.