A unicycle is a human-powered, single-track vehicle with one wheel. Unicycles resemble bicycles, but are less complex. One theory of the advent of the unicycle stems from the popularity of the penny-farthing (or 'Ordinary') during the late 19th century. Since the pedal and cranks were connected directly to the front axle, the rear wheel would go up in the air and the rider would be moved slightly forward. Many penny-farthing owners discovered they could dispense with the frame and just ride the front wheel and handlebars. Evidence for this theory of development can reportedly be found in pictures from the late 19th century showing unicycles with large wheels. Over the years, unicycle enthusiasts have inspired manufacturers to create new designs, such as seatless ('ultimate wheel') and tall ('giraffe') unicycles. During the late 1980s some extreme sportsmen took an interest in the unicycle and started off-road unicycling ('MUni', or 'mountain unicycling').
Contributions by AndrewDressel, 184.108.40.206, and Merphant.