Wisconsin Central and Wig Wags at Fond du Lac.

The old wig wag style grade crossing signal is now virtually extinct. However, in the 1990s, a fair number of these signals could still be found in Wisconsin.

This is an excerpt from my book Railroad Signaling (first published by MBI 2003):

One of the first standard types of automated visual grade crossing warning was the automatic flagman, a signal commonly known as a ‘wig wag’. [This was] adopted as a standard crossing device by the American Railway Association in 1923. A standard wig wag is actuated by a track circuit and consists of a paddle with a red lamp that gracefully swings back and forth in a horizontal pattern when a train approaches [and] usually accompanied by a bell . . . [at one time] the wig wag was the preferred type of grade crossing protection in the Midwest and far west. [They were] largely supplanted by modern flashing signals and crossing gates.
Exposed on Fujichrome Provia 100 using a Nikon F3T with an f1.8 105mm Nikkor lens.

I was traveling with Marshall Beecher on the morning of August 3, 1996, when I exposed this view of Wisconsin Central’s southward freight ANPR-A approaching a grade crossing on the former Chicago & North Western line in Fond du Lac. This line saw less traffic than WC’s near by former Soo Line mainline over Byron Hill, but the attraction was these antique signals. Notice my use of selective depth of field.

Tracking the Light is Daily.