This two-ton Holstein was erected in 1969 to promote Ehlenbach's Cheese Chalet and was named in honor of the store's first owner, Lucille (Sis) Ehlenbach. According to her Facebook page (really!), Sissy used to be able to deliver an impressive moo, the speaker no longer works but there are plans to restore her voice.
If you go:
With a choice of more than 100 different Wisconsin cheeses, Ehlenbach's itself is worth a visit too whilst you're here.
Links:

4879 County Rd V
Exit 126, Jct V & I90-94
DeForest, Wisconsin 53532 USA
Phone Numbers:
Ehlenbach's Cheese Chalet
+1 (608) 846-4791
+1 (608) 846-4791