For over 90 years, this classic Midwestern interlocking tower protected the junction of the Milwaukee Road and the Elgin, Joliet & Eastern at Spaulding, just east of Elgin, Illinois.
Originally built around 1890 when the EJ&E extended north toward Waukegan, the tower was expanded to its present size when the Milwaukee Road added a second main and a yard lead in 1909. It housed a 36-lever hand-operated interlocking machine to control all of the track switches and signals at Spaulding. The junction was converted to centralized control and the tower closed in the 1980's.
Spaulding Tower was donated to IRM in 1988 by the EJ&E and by Metra and the Soo Line, which took over the Milwaukee Road route after the line's bankruptcy. IRM volunteers dismantled the huge interlocking machine before the upper story of the building was cut off, and both halves were moved by truck to Union. IRM crews reassembled the building and restored it to its 1950's appearance.
Towers and Interlocking Plants
Where railroads cross at the same level ("at grade") or another route branches off, there must be some means to prevent collisions.
At one time, nearly every junction had an adjacent tower housing an operator. The tower operators controlled the track switches and signals governing the route of each train through the junction. The controls were "interlocked" to prevent potential conflicts; if one train was given a "Clear" signal, the controls physically prevented a "Clear" indication on any opposing route. Early towers had a series of large mechanical "Armstrong" (hand-thrown) levers, whose motion when thrown was transmitted by a series of moving rods to change the position of track switches. Modern interlocking plants used electric or pneumatic power rather than hand-thrown levers.
By the late 1900's, manned towers had nearly disappeared except at busy urban terminals. Today, a dispatcher who may be hundreds of miles away can control all switches and signals electronically.