Since the construction of the Columbia & Port Deposit Railroad in 1877 trains have operated through Safe Harbor, where the Conestoga River joins the Susquehanna. When construction of the A&S began in 1902 the route was planned to diverge from the Port Road six miles north at Creswell beginning a gentle climb out of the Susquehanna Valley. The first formidable obstacles the PRR would encounter on the new alignment would be the approach and spanning of the Conestoga River Valley. Beginning excavation in 1903 contractor H. S. Kerbaugh converted a former rolling mill in Safe Harbor to provide compressed air to drill pilot holes for blasting in the rock face high above. The dynamite would be hoisted up the cliffs by hand, detonated and the process was repeated. The resulting debris caused the Port Road below to be closed for extended periods of time due to the dangerous conditions, which often buried the right of way.
Perhaps one of the more dramatic locations on the PRR, the new A&S Bridge would stretch 1560’ in length at roughly 100’ higher than the Port Road below. While construction was underway on the new span a flood in 1904 would destroy the Port Road Bridge. Taking advantage of the ongoing construction, engineers decided to incorporate a new crossing on the Port Road, rather than rebuild the existing stone arch bridge. The new span would provide a stronger bridge for the growing freight traffic with the added benefit of increased clearance from the Conestoga River below.
Chief Engineer, William H. Brown would design the bridges utilizing different style spans to meet the specific needs of each route. The A&S bridge, much longer in length included a 300’ pin connected Pratt deck truss over the river supplemented by plate girder viaducts on steel bents - nine spans measuring 480’ to the north and seventeen spans to south measuring 780’. The bridge would carry two main tracks at height of almost 150 above the creek. Down below on the Port Road, the new bridge would feature 3 riveted deck plate girder spans carrying the two main tracks at a height of 55’ above the 1905 water line.
The steel work for the bridge was fabricated in Steelton by PRR owned subsidiary Pennsylvania Steel and was erected by contractor H.S. Kerbaugh Inc. who had been one of two key contractors during the A&S project. The construction of the masonry piers and retaining walls was unique in that the upper and lower spans shared a monolithic L shaped pier on either side of the river. The piers for the main A&S span went up as the falsework was constructed to support the new 300’ Pratt deck truss, once this was completed, assembly of the approach viaducts proceeded, the northern first then the southern approach. When the majority of the high level erection was completed, contractors could commence work on the lower level Port Road bridge. By July of 1906, trains were running on the A&S and the Port Road, which had suffered from months of closure and restriction due to the construction, would finally resume normal operations later that year in August.
In 1930 construction would commence to build the northern most of three Depression Era hydroelectric dams along the Susquehanna River at Safe Harbor. Erected just above the confluence of the Conestoga River the first turbine went online in December of 1931 and by 1940 a total of seven were in operation. Two of these turbines were dedicated to generating the 25 Hz single-phase power required to feed the Pennsylvania Railroad’s newly electrified railroad. By 1938, the final phases of the electrification were complete and included the A&S, Port Road, Columbia branch and mainline west to Harrisburg. With the eastern mainline and freight network complete, power from Safe Harbor began supplying the PRR grid, with tethers of high voltage transmission lines mounted above the tracks, feeding various substations along the PRR’s electrified territory. The railroad understood the value of the Public Works project and the advantage of a renewable energy source. Today Safe Harbor operates 12 turbine generator units and continues to supply the Northeast passenger rail network today.