During the age of the steam locomotive coaling towers were an essential part of railroading as without them there was little way to effectively fuel the motive power. The coal chute or coaling station,
as it is also sometimes known, dates back to the late 1800s as steam
locomotives became larger and required a larger fuel capacity. As with
steamers themselves there were all different sizes of towers and they became much larger into the 20th century. Some of the last towers ever built were from reinforced concrete and stood hundreds of feet tall.
They were so well built that several still stand to this day, over a half-century since they were last used! Interlocking towers
(known as a signal box on English railroads) were once a vital
component of the railroad network centralizing a group of signals at a
busy location of a main line (such as a junction, crossover, diamond,
etc.) into one location with an operator who would manually set the
signal(s) to the appropriate reading (proceed, stop, caution, etc.). Some railroads had their own names for interlocking towers,
such as the Chesapeake & Ohio Railway which called them cabins. As
the 20th century wore on improved technologies allowed for dispatching
and signal control to be centralized and not so localized for a given
section of railroad track.
As such there was no longer a need for interlocking towers and today's popular centralized traffic control or CTC has all but done away with them. You can still find a few towers guarding particular locations, such as the busy intersection of Fostoria, Ohio. However, by and large the interlocking tower is a very endangered species that will soon be extinct. During the Golden Age, or classic era, of railroading one could find all types of lineside structures in use like those mentioned above. During those days virtually every job required a human, or at least someone to keep a watchful eye out. As technologies have improved many of these jobs are no longer needed, like the crossing watchmen, resulting in many of these buildings to likewise be of little use. Of course, for railroads it was a way to reduce costs not only in fewer individuals on the payroll but also lower property taxes.
If you are interested in fallen flags and classic systems before the modern merger movement took hold I would suggest purchasing one, or all three volumes of Mike Schafer’s Classic American Railroads series of books. The publications feature a wealth of information and are loaded with colored photographs covering names like the Baltimore & Ohio, Santa Fe, Pennsylvania, Milwaukee Road, and lots more. If you have any interest in most famous bygone railroads which once operated in the U.S. I would strongly recommend picking up one, two, or even all three of Mr. Schafer’s book. I truly cannot say enough just how enjoyable and fun they are to read and peruse through.