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Deibler Gap Road Bridge

(Dauphin County Bridge No. 27, Seaman Bridge)

  • Year Built: 1900
  • Type: Baltimore Thru Truss
  • Number of Spans: 1
  • Length: 162'5"
  • Width: 17'2"
  • Builder: Chambersburg Bridge Company
  • Location: Mifflin Township, Dauphin County
  • Carried: Deibler Gap Road (TR 474) over Mahantango Creek
  • Preservation Assistance: Unknown
  • BRKey: 14693


The Deibler Gap Road Bridge is a pin-connected Baltimore thru truss built in 1900 by the Chambersburg Bridge Company. This single-span bridge is 162'5" long and 17'2" wide with a vertical clearance of 12'. It is located in Mifflin Township, Dauphin County, where it carried Deibler Gap Road (TR 474) over Mahantango Creek until it was closed to vehicular traffic in 1983. This bridge is listed in the National Register of Historic Places.

The character-defining features of this bridge include the truss form (Baltimore thru), method of truss member end connection (pinned), structural members to include the top and bottom chords, vertical and diagonal members, sway bracing, and features of the portal.  An unusual feature of this bridge is the riveted plate floorbeam connection.

To preserve this historic structure, ownership of the bridge in its entirety will be transferred to an interested party for removal to a new location. The new owner will be responsible for costs associated with removal, rehabilitation and long-term maintenance of the structure. If you or your organization is interested in assuming ownership of this historic bridge, please contact Tyra Guyton of the Pennsylvania State Historic Preservation Office at or at (717) 346-0617 or Jeremy Ammerman of PennDOT District 8 at or at (717) 705 - 2667.