Mystic River Railroad Bridge

The Mystic River Railroad Bridge carries Amtrak’s Northeast Corridor over the Mystic River at Mystic, Connecticut. The present structure, a Warren through truss swing span completed in 1982, replaced a steel center-bearing swing bridge of 1919 built for the New York, New Haven and Hartford Railroad.

The Shore Line Route

Steamship lines covered Long Island Sound throughout the 19th century, and the impetus for a through rail route along the Connecticut shore therefore developed relatively late in the history of New England railroading. ¹ Two inland routes, the Willimantic, Providence & Boston and the Springfield line by way of Hartford, Connecticut, and Springfield, Massachusetts, already connected New Haven and Boston at approximately the same distance in rail miles. An all-rail shore line route was not completed until 1889. Movable bridge technology advanced considerably at about the same time. As the older crossings along the shore line deteriorated and became inadequate for heavier and faster traffic, they were replaced with new movable spans representative of contemporary practice.

The New York, New Haven & Hartford Railroad

The New York, New Haven & Hartford Railroad was formed by the consolidation of the Hartford & New Haven Railroad Company with the New York & New Haven Company. ¹ The two railroads entered into a partnership agreement, the capital was divided, and the new company was established on August 6, 1892.

By the end of the 19th century the New York, New Haven & Hartford extended from New York to Boston and virtually controlled rail traffic in southern New England, effectively preventing any further major competition along its lines. The company then moved to secure that position through a building program carried out largely between 1911 and 1919.

Among the earliest movable crossings in the United States were a series of parallel swing bridges built across the Charles River in Boston in the early 19th century. ¹ These were timber trusses hinged at one end that swung open to leave a narrow channel for navigation. Many rim-bearing swing bridges were built in the Mississippi Valley during the 1860s. The center-bearing swing bridge, superior to the rim-bearing type in many respects, was improved substantially between the late 1880s and 1900. After 1900 the strong advocacy of C. C. Schneider, a consulting engineer for the American Bridge Company, influenced many engineers to adopt it. More modern bascule and vertical lift types were not developed until after 1890, following the refinement of the electric motor and the development of a workable method of counterbalancing the weight of a large span.

The large number of navigable rivers and inlets to be crossed along the eastern seaboard resulted in fifteen movable bridges on what is today the Northeast Corridor: nine bascule bridges, five swing bridges, and one vertical lift bridge. ¹ Swing spans were generally preferred where the waterway was wide enough to allow clearance on either side. Where it was too narrow, as was often the case in the northeast, vertical lift or bascule bridges were used instead.

The Mystic River bridge was one of four movable bridges built by the New York, New Haven & Hartford Railroad along the shore line. ¹ The spans were prefabricated at the construction company’s plant and then erected on site by unskilled labor. The operating machinery was not standardized, and each bridge had its own mechanical components.

The earliest bridge over the Mystic River was a single-track wooden drawbridge built in 1819. ¹ An iron bridge followed in 1866, and a new drawbridge was erected in 1905 by the Berlin Construction Company. The center pier and some of the trestles of the 1905 structure were incorporated into the bridge that succeeded it.

While the New York, New Haven & Hartford was building a new bridge at Groton, it was also planning and constructing a replacement crossing of the Mystic River. ¹ The structure was designed in 1917 at the Edgemoor plant of the American Bridge Company under the direction of Mr. Searles, Chief Engineer, and W. H. Moore, Bridge Engineer for the railroad. The Pencoyd plant of the American Bridge Company fabricated the machinery. The completed bridge, a steel center-bearing Warren through truss swing span, entered service in 1919.

The structure measured 277 feet overall. The swing span was 181 feet long and carried two tracks on stringers and floor beams framed into the lower chord of the trusses. ¹ The center pier was circular and built of stone, and the drive machinery was placed below track level above the pier. By the time the Mystic bridge was designed and built, the rim-bearing type had fallen into some disfavor on account of its complicated machinery and the difficulties encountered in maintenance and repair.

The interlocking at Mystic was regarded as no less significant than the bridge itself. ¹ It performed its functions electrically and consisted of a “Style B” electro-mechanical interlocking machine manufactured by the Union Switch & Signal Company of Swissvale, Pennsylvania, and first placed in service in October 1906. The machine controlled the switches, derails, bridge locks, and H-5 searchlight signals, the last of which used a lamp and lens system to project three colors and had replaced earlier semaphore signals. Designed by one of the foremost signal companies of the 19th and 20th centuries, it carried 29 levers, of which 11 remained in use, and it was the only machine of its kind on the Northeast Corridor. It had not been altered since installation. The machine governed one mainline crossover and one mainline turnout in addition to the bridge interlocks and signals, and the interlocking house contained the reversing drum controllers for the turn and lock motors, foot-operated limit override switches, a meter board, disconnect switches, a signal model board, and signal lock relays.

The 1919 bridge underwent repeated repairs. ¹ The stringers, stairways, railings, and top laterals were repaired in 1945. Further work was carried out on the center pier in 1951 and 1955, and the machinery and center fenders were repaired in 1956.

The New York, New Haven & Hartford Railroad was absorbed into the Penn Central Railroad following that company’s 1969 merger. ¹ After Penn Central’s bankruptcy, ownership of the bridge and the surrounding Northeast Corridor infrastructure passed to the National Railroad Passenger Corporation, known as Amtrak, in 1976.

The structure eventually deteriorated to the point that replacement was judged necessary in order to improve operational reliability for the railroad. The bridge was replaced in 1982 under the Northeast Corridor Improvement Project by a new Warren through truss swing span of similar design.

Today, the two tracks carried over the bridge are owned by Amtrak as part of the Northeast Corridor and are used for Northeast Regional and Acela Express services. ¹ A proposal to extend Shore Line East commuter rail service from its present terminus at New London to Mystic will require use of the crossing as well.