July 31st
Now in its 44th year, the Yellowstone Rod Run annually draws five to seven hundred street rods from all over the United States. Cruises and various competitions are available to registrants. Saturday's Parade of Rods on Canyon Street is an event highlight. The Show & Shine in City Park, where a festival atmosphere prevails, is also on Saturday and is open and free to the public.
http://www.yellowstonerodrun.com/