[7] It was built as a steel arch continuous through truss bridge that spanned the lower Patapsco River and outer Baltimore Harbor/Port in Maryland, United States.

Initially named the Outer Harbor Crossing, the bridge was renamed in 1976 for poet Francis Scott Key, who wrote the lyrics to "The Star-Spangled Banner", the U.S. national anthem.

In October 1968, this Outer Harbor Tunnel project received financing through a $220 million bond issue (equivalent to $1.9 billion in 2023) that also funded the twinning of the Chesapeake Bay Bridge.

[13] So officials drafted alternative proposals, including a four-lane bridge, which had the advantage of providing a route across Baltimore Harbor for vehicles carrying hazardous materials barred from tunnels.

[15][16] The United States Coast Guard issued a bridge permit in June 1972, replacing the earlier approval of the tunnel by the Army Corps of Engineers.

These piers also had 17-foot fender system:[20] crushable thin-walled concrete boxes of 100 by 84.5 feet, clad with timber members and steel plate at the base.

[21] In 1976, as construction went on, the bridge was named for Francis Scott Key, the author of "The Defence of Fort M'Henry", the poem upon which "The Star-Spangled Banner" is based.

[22] Key had been aboard an American truce ship with the British Royal Navy fleet in Baltimore Harbor near Sollers Point; the approximate location is within 100 yards (91 m) of the bridge and marked by a buoy in the colors of the U.S.

[24] In 1978, the bridge received an Award of Merit from the American Institute of Steel Construction in the Long Span category.

[45] Hours after the collapse, President Joe Biden said that the federal government would pay for the entire cost of reconstructing the bridge.

Work on the new bridge is scheduled to start January 7, 2025, after the approval by Congress of the December 2024 continuing resolution which included $2 billion in funding.