There is a set of active wig-wags on Water Street in Lewistown,
Montana. These are ex-Milwaukee WRRS Harpes wig-wags. The branchline (for now) is operated by the BNSF railway. These are the only ex-Milwaukee wig-wags in service in the west to my knowledge. 

There is rumors that Lewistown does not want tracks in town anymore and
BNSF may abandoned the line anyway as it sees very little traffic. When
I saw it in action the train consisted of 4 engines 1 flatcar with a
John Deer Combine and a caboose in; 4 engines, a loaded chip car, and
caboose out. The train schedule can very. The Lewistown Local runs out
of Great Falls (usually early Thursday morning, sometimes Wednesday) and
ties up in Lewistown  around noon or afternoon. They leave town and head
back to Great Falls early the next day.

To get to the wig-wags take Hwy. 87/191/200 into town. Once you have
reach the grade crossing turn right (south) and go three blocks to Water
street. Go back to the tracks on Water Street. Can't miss them, most
interesting site for hundreds and hundreds of miles around.