Running over 53 miles in length the PRR's Atglen & Susquehanna Branch was a shining example of modern railway construction, running across rolling countryside and up the Susquehanna River on a gentle gradient. Fittingly for such a contemporary piece of railroad engineering, another advancement of modern times accompanied the line; the telephone. By the time the A&S opened for business in 1906, the PRR was rapidly working towards constructing one of the world's largest private telephone networks, laying cable along its system for critical functions like dispatching trains in addition to providing an extensive "in-house" communication network. The PRR's interest in telephone technology dates back to 1877 when officials invited Thomas A. Watson, assistant to Alexander Graham Bell for a demonstration in Altoona. While the railroad made a modest investment for non-critical communication following this meeting, it wouldn't be until 1897 when the technology was employed to dispatch trains entirely by phone on the South Fork Branch of the Pittsburgh Division.
As technology was improved, the PRR began investing heavily in building a communication network, and by 1920 almost the entire system was dispatched by telephone. East of Paoli in the electrified territory, cable was laid in an underground duct system, west of Paoli the cable lines were often above ground on lineside poles and west of Harrisburg an extensive line side open wire system was employed. By 1955 the PRR boasted some impressive statistics in their company magazine, The Pennsy stating, "Today the PRR's network is generally accepted to be the largest private telephone system in the world. Its transmission lines stretch 41,000 miles. It's cost, together with that of the associated Teletype network, totals $35 million. On any typical day, PRR lines carry an estimated half-million calls."
With the start of operations, the A&S was dispatched by phone from Harrisburg, out on the line local control via eight block stations provided the means for changing tracks and relay orders to passing trains. These included Parkesburg (PG), Atglen (NI), Quarryville (Q), Shenks Ferry - (SF - later Smith), Cresswell (CO), Columbia (LG-42), Marietta (RQ) and Wago Junction (WJ). Additionally, the PRR constructed 11 watch boxes along the A&S that were staffed 24/7 due to the continuous risk of washouts and cave-ins with the numerous cuts, fills, culverts and bridges along the line. Track inspectors could reach dispatchers via the watch boxes or line side phone boxes spaced roughly every 1.25 miles for field access in the event a situation should arise.
Consolidation of block station and train order offices began during the Depression, with Quarryville placed out of service on August 11th, 1928. More change in operations came with the final phase of electrification completed in 1938. The project, which included the installation of automatic block signals and the implementation of established Current of Traffic Rule 251 eliminating the need for intermediate manned block stations. An additional benefit of the signal system was the integration of slide detector fences in areas prone to rockslides, eliminating the need for staffed watch boxes. Cola tower opened in Columbia sporting a 120 lever centralized traffic control machine, dispatching over 175 miles of freight only territory. Under its jurisdiction on the A&S were Cresswell, LG-42 and Marietta (Shocks) as well as trackage down the Port Road south to Holtwood. Parkesburg was also rebuilt, relocated to a one of a kind brick single story building, containing a 39-lever Union Switch & Signal Model P interlocking machine. The last block station of note proved to be a bit of mystery, NI at Atglen just a few miles west of Parkesburg closed sometime between 1928 and 1945 based on various employee resources, but at this time I have found little else to narrow the dates of its demise. By the time electrification was complete all but one remaining manned block station survived on the A&S between Parkesburg and Cola; Shenks Ferry (SF), later renamed Smith, was retained as a part-time facility due to its location approximately midway between Cress and Parkesburg. While Smith ultimately met its demise, Cola survived into the Conrail era, closing in March of 1987, followed by the A&S in 1988. On the opposite end of the line, Parkesburg survived well into the 21st Century under Amtrak. The closing of Parkesburg during the Keystone Corridor improvements was the first in a string of tower closures that mark the end of an era in technology and dispatching that lasted longer than the company that helped pioneer the technology.