Iverider
Cruisin' on my Bluebird
In 1974 Gary Fisher took a 1937 Schwinn Excelsior frame and basically invented the modern mountain bike. This first bike was called a Klunker.
see link.
http://www.tomligon.com/garyfisher.htm
Yes, Prior to this, no one EVER rode a balloon tire or any other bicycle off road.