over for construction of Interstate 395. The tunnel is brick-lined with iron-arched centerings. At the time of completion it was considered innovative for its use of electricity for illumination and powering of locomotives. Inside the tunnel, there was an underground platform for trains serving Camden Station. The Howard Street Tunnel is listed on the National Register of Historic Places. Electrification By this time the Pennsylvania Railroad line through Baltimore and points south had been in operation for twenty years. Due to the built-up nature of the area traversed and the hilly terrain, much of its line through town was in tunnels, which posed severe ventilation problems. Large chimneys were constructed above the Pennsylvania line, in a not entirely successful attempt to disperse the fumes from the coal-fired locomotives. However, by 1890 electric locomotion was beginning to appear possible, and in 1892 the B&O thus contracted with General Electric (GE) for electric locomotives, powerhouse equipment, and an electrical distribution system. This equipment was delivered beginning in 1895, and the first train pulled by an electric locomotive operated through the Howard Street Tunnel on June 27, 1895. The grade on the electrified portion was downhill to Camden Station; therefore traffic heading southbound ("westbound", in B&O timetables), from Mount Royal Station, simply drifted through the tunnels. Since the engine was not working, the smoke produced was relatively light. Going upgrade northbound ("eastbound", in B&O timetables) the electric locomotives were coupled to the front of the train at Camden Station and pulled the entire train, including the steam locomotive, through the Howard Street tunnel. When northbound passenger trains stopped at Mt. Royal Station at the north end of the tunnel, the electric locomotive was uncoupled. Northbound freight trains were pulled by electric locomotives for another two miles, until reaching Huntingdon Avenue in east Baltimore. There the steam locomotive closed its cylinder cocks, took up the load, and the electric locomotive uncoupled on the fly, accelerating ahead to a pocket siding between the tracks. General Electric installed rotary converters in B&O's powerhouse near Mt. Royal Station, having a combined capacity of 5,000 kW to convert 13,200-volt, 3 phase, 25-cycle AC to 675 volts DC. In 1936, these rotary converters were replaced by mercury arc rectifiers. Initially power was supplied through a unique system in which a pickup shoe rode in a channel above and to one side of the track. This proved vulnerable to contamination