historic context of maryland highway bridges built between 1948 ...

SECTIONSIXResults of Field Investigationsmid-twentieth century. The use of truss technology is increasingly rare in Maryland after WorldWar II and thus a truss bridge from this period would more likely be considered eligible for theNational Register under Criterion C than would a similar bridge from the pre-World War IIperiod. The MD 144 Bridge over the Monocacy River (Bridge 1003803) in Frederick County isNational Register-eligible under Criterion C on the state level, as it is one of only two deck trusshighway bridges built in Maryland during the 1948-1960 period, and is distinguished by itsarched Warren truss design.Metal truss bridges may also be considered eligible if they reflect a unique design or a significantdevelopment in the history of bridge engineering (Spero and Berger & Associates 1995: C-14).One such bridge is the I 895 Bridge (BC07800) over the CSX tracks in Baltimore County whichis National Register-eligible under Criterion C on the state level as the only highway bridgeusing a ―K‖ truss design built in Maryland.Historic research also can reveal the bridge‘s attribution to a particular designer, design firm, orgovernment entity. This is particularly true for bridges not prepared according to standardizedplans or that spanned particularly challenging waterways or land forms. In these cases, the StateRoads Commission usually contracted out the bridge design to a commercial engineering designfirm, such as the well-known J.E. Greiner firm of Baltimore. The Wise Avenue over Bear CreekBridge (B0079) in Baltimore is National Register-eligible under Criterion C, not only as a rareexample of a bascule bridge in Maryland, but also for its design association with the J.E. Greinerfirm.A bridge may be National Register-eligible if it is associated with designers who developedpatented or proprietary bridge features. These bridge types may be examples of rare or commontypes used on spans across the State of Maryland. The Kent Narrows Bridge (Bridge 1700600) inQueen Anne‘s County is National Register-eligible under Criterion C as it is one of only twomovable bridges in Maryland designed by the New York engineering firm of Hardesty &Hanover. Hardesty & Hanover and its predecessor firms were national leaders in thedevelopment of movable bridge technology from the late nineteenth century through the present.Carrying equal weight with a bridge‘s historical (Criterion A or B) or engineering significance(Criterion C) is the bridge‘s integrity. Integrity is usually defined as the ability of a resource toconvey its historical significance. Within the concept of integrity, the National Register Criteriarecognize seven aspects of integrity that in various degrees define integrity: location, design,workmanship, materials, setting, feeling, and association.In evaluating the aspects of integrity for a historic bridge, it is necessary to define those characterdefining elements of a bridge which are necessary components of its type. The most prominentfeature of a metal arch bridge is its bowstring arch, but additional elements include the approachspans, the substructure of piers and abutments, and the railing if any. Character-definingelements of a concrete beam bridge would include the superstructure of slab, beams, and parapet,and the substructure elements of abutments and piers. Alterations of these features detract fromthe integrity of the bridge as a whole and thus its National Register eligibility, while meresurface changes such as a redecking of a truss bridge would not.\15-SEP-11\\ 7-3