Exterior styling is primarily Colonial Revival, having Flemish bond brickwork and a soldier course belt rail separating floors. A bay on the second story facing the tracks, faced with cut stone, is a function of the building's use rather than a style element. End walls rise above the roof line and are capped with concrete parapets. The majority of windows have concrete keystones. The basement walls are concrete also.
Structural integrity is good.
Statement of Significance Harris switch tower is an example of a railroad interlocking tower. The function of an interlocking tower is to provide control over a junction of track switches, which allow trains to change course or direction, and lineside signals, which control trains' speed. In 1946 there were almost 550 of these structures lining the tracks of the Pennsylvania Railroad, and 4400 in the nation. Harris tower stands one block north of the Harrisburg passenger station, whose 1887 brick building and Fink truss train sheds are listed on the National Register, and once controlled all train activity just to the north of the station. Today, although 17 passenger trains arrive or depart Harrisburg daily, just two come under Harris tower's control.