Perhaps the bane of Chief Engineer William H. Brown's existence, the Shocks Mill Bridge is of significant note among the countless stone arch bridges, overpasses and culverts constructed on the PRR during his tenure. Opened in 1903 the Shocks Mills bridge was a part of the low-grade freight only line being constructed to connect Philadelphia and Harrisburg. Situated roughly 8 miles railroad west of Columbia the strategic bridge and accompanying line linked the Northern Central in Wago with existing lines in Columbia and ultimately the new Atglen and Susquehanna further down river. The 28 arch stone bridge was over 2200 feet long spanning the Susquehanna River with trains riding approximately 60 feet above low water. A smaller sister to the beautiful Rockville Bridge further upstream, initial construction cost the PRR $1 million dollars to build the bridge and long fill on the eastern approach. However problems with the bridge developed when piers began to settling in 1904 resulting in more money and time spent to reinforce the compromised areas of the span. After this additional work the bridge endured decades of heavy use and the additional of catenary during the later electrification phase of freight lines in 1937-38.
In June of 1972, Hurricane Agnes would batter the East Coast causing record floods throughout the area resulting in over 3 billion dollars in damage and causing over 128 fatalities. Cash starved Penn Central was hit hard having multiple washouts throughout the system but one of more significant would be the loss at Shocks Mill. On July 2nd, 1972 a train crew noticed problems with the center piers of the bridge as flood waters raged below during one of the worst natural disasters in American history. Soon after, six piers toward the center of the stone bridge would collapse rendering the low-grade line useless until the damage could be assessed and rebuilding could take place. Becuase the PC was under bankruptcy protection court permission was sought to rebuild the vital link. Started late in the third quarter of 1972 the new construction was completed by August of 1973 utilizing nine new concrete piers supporting deck girder spans to bridge the void. Until settling compromised a pier on the Rockville bridge in 1997 this would be the only major failure on record of the proven and sturdy construction methods Brown used during his 25 year tenure as Chief Engineer.