Fort McHenry Tunnel

The Fort McHenry Tunnel is one of two tunnels that carry traffic underneath the Baltimore Harbor. It is named for Fort McHenry, which it passes close by.

The tunnel, opened on November 23, 1985, closed a gap in the East Coast’s most important interstate route, Interstate 95, between Maine and Florida. It also is the largest underwater highway tunnel built by the immersed tube method and the widest vehicular tunnel ever built by that same method. 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 is one of seven toll facilities operated and maintained by the Maryland Transportation Authority.

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 2010 the toll rate for cars is $2.00, paid in either direction. Vehicles with more than two axles pay additional amounts, up to $15.00 for six axles.


Originally, plans called for an eight-lane bridge across the Baltimore Harbor to complete the final section of Interstate 95 in Maryland. However, it was next determined that a bridge would have had a negative environmental and aesthetic impact on the nearby National Monument and Historic Site at Fort McHenry, and also on the neighboring residential communities of Locust Point and Fells Point. An eight-lane, 1.5-mile (2.4 km) tunnel was proposed as an alternative.


The tunnel, as completed, extends from the Locust Point peninsula, passes south of Fort McHenry under the harbor navigational channel, and rises to surface grade in the Canton industrial area of Southeast Baltimore. (Ironically, a tunnel was originally proposed for the final section of Interstate 695 to be completed between Curtis Bay and Dundalk, Maryland, before the alternative that would be known as the Francis Scott Key Bridge was selected.)

Design and construction

The tunnel's route near Fort McHenry and below the shipping channel prompted the design of the world’s first tunnel sections that curved both vertically and horizontally. The tunnel sections were manufactured in Port Deposit, Maryland, and they were floated to the site using tugboats.

The tunnel was built using the open-trench method, in which prefabricated tunnel sections were sunk in a trench dredged in the harbor’s bottom. The sections were then joined underwater. A dredge-disposal site for materials removed from the tunnel trench was created at the nearby Helen Delich Bentley Port of Baltimore, resulting in 136 acres (55 ha) of new, usable land for the Seagirt Marine Terminal. 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 and Interstate 895, which had opened to traffic in 1957, were closed for extensive rehabilitation.

Before and during the Civil War, a tunnel had been dug from the Baltimore and Ohio Railroad's Camden Station south to the north side of Federal Hill, and then to Fort McHenry. During the construction of the Fort McHenry Tunnel, some houses in the Federal Hill neighborhood collapsed when that brick-lined tunnel collapsed. That tunnel was probably built by the U.S. Army and fell from use after the Civil War.


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