The Francis Scott Key Bridge: Construction and Traffic

On March 23, 1977, the Francis Scott Key Bridge opened to traffic across Baltimore’s outer harbor in Maryland, completing the final connection of the Baltimore Beltway. Crossing the Patapsco River, it linked industrial districts on both sides of the port with the Beltway. The original bridge remained in use until 2024.

The Maryland Transportation Authority’s construction financial records describe the river crossing and its approaches from Hawkins Point in Baltimore City to the vicinity of Sparrows Point in Baltimore County. The overall project also included a movable bridge over Curtis Creek, the Bear Creek bridge and roads serving the Sparrows Point industrial district.

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The Maryland Transportation Authority owned and operated the bridge. The American Institute of Steel Construction’s 1978 prize-bridge list identifies Greiner Engineering Sciences as engineering consultant, with Singstad, Kehart, November & Hurka and Baltimore Transportation Associates also participating in design. Several specialist organizations divided the design, fabrication and erection work.

Pittsburgh–Des Moines Steel was listed as contractor and steel fabricator, while John F. Beasley Construction erected the structure. Separate organizations handled steel production and installation on site, forming the main production chain for the large harbor crossing. The completed bridge received the institute’s 1978 Award of Merit in the long-span category.

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A continuous steel through-truss crossed the main navigation channel, with a central span of 1,200 feet, approximately 366 meters, and two back spans of approximately 722 feet each. The roadway passed through the truss, while multibeam plate-girder structures formed the northern and southern approaches. The truss crossed the principal channel, with the approaches connecting the bank-side roads to it.

Crossing an active harbor channel meant accommodating both road loads and shipping space. The National Transportation Safety Board records approximately 185 feet of vertical navigation clearance and 1,100 feet of horizontal clearance between the supporting piers. A long main span and elevated deck provided passage for ships, while requiring the approaches to raise the roadway gradually to deck level.

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Alongside the steel truss, deck material was an important part of the long-span design. A 2021 Federal Highway Administration report explains that the main bridge used structural lightweight concrete to reduce dead load and allow longer spans. It gives a fresh-concrete unit weight of 112 pounds per cubic foot and a specified compressive strength of 4,000 pounds per square inch.

Construction funding formed part of Maryland’s toll-bridge and tunnel financing system. The report submitted to the trustee bank in 1977 states that bridge and tunnel revenue bonds of $220 million issued in 1968 and $34 million issued in 1975 jointly supported several projects, including the parallel Bay Bridge and outer-harbor crossing. This arrangement linked bridge construction with toll revenue and long-term debt repayment.

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After opening, the bridge became part of Baltimore’s harbor-crossing network, serving local and interstate traffic alongside the Harbor Tunnel and the later Fort McHenry Tunnel. It also provided a route for hazardous-cargo vehicles, which could not use the tunnels beneath the harbor. The bridge gave this freight a route around the port.

The Maryland Transportation Authority’s fiscal 2003 financial statements record approximately 11.55 million vehicle passages across the bridge that year. Operations continued to change: in October 2003, the speed limit in dedicated electronic-toll lanes increased from 15 to 30 miles per hour. Attention had shifted from completing a crossing to reducing stops and queues at the toll plaza.

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Independent protective dolphins were built near the main piers, with concrete and timber fender systems surrounding the piers themselves. On March 26, 2024, the containership Dali lost electrical power, propulsion and steering ability, and struck pier 17 supporting the main span. Much of the bridge collapsed, killing six road workers and ending the original crossing’s service.

The NTSB’s 2025 board-meeting summary identifies a power loss caused by a loose signal-wire connection aboard the ship as the accident’s cause, and points to inadequate mitigation of ship-collision risk and emergency-evacuation communications for workers. The 1977 project successfully completed the Beltway connection, while its long service also showed the need to consider the road structure, harbor shipping and collision-protection management within the same transport environment.

References: [5] [6]