4000 artifacts chronically the evolution of the bicycle along with space memorabilia from Deke Slayton's collection are found here. Plus there is a collection of aviation gear from Monroe County. The slogan of the museum is 'From Sprockets to Rockets.'
If you go:
Be sure to watch the vintage (1960's) bike safety film 'One Got Fat', which the museum screens regularly. As even the staff will tell you, it's a priceless and unintentionally amusing gem of training film schlock, with a rather macabre approach to warning kids to ride their bikes responsibly.
Links:

200 West Main Street
Sparta, Wisconsin 54656 USA
dekeslayton@centurytel.net
Phone Numbers:
Museum Information
+1 (608) 269-0033
+1 (608) 269-0033