Older snowmobiles could generally accommodate two people; however, most snowmobiles manufactured in the last twenty-five years have been designed for a single rider. Snowmobiles built with the ability to carry two riders are referred to as "2-up" snowmobiles or 'touring' models and make up an extremely small share of the market. Snowmobiles do not have any enclosures, except for a windshield, and their engines normally drive a continuous track at the rear. Skis at the front provide directional control.
Early snowmobiles used rubber tracks, but modern snowmobiles' tracks are typically made of a Kevlar composite. Originally, snowmobiles were powered by two-stroke gasoline internal combustion engines and since the mid-2000s four-stroke engines have also entered the market.
The second half of the 20th century saw the rise of recreational snowmobiling, whose riders are called snowmobilers or sledders. Recreational riding is known as snowcross/racing, trail riding, freestyle, mountain climbing, boondocking, carving, ditchbanging and grass drags. In the summertime snowmobilers can drag race on grass, asphalt strips, or even across water (see Snowmobile skipping). Snowmobiles are sometimes modified to compete in long-distance off-road races.
In 1915 Ray H. Muscott of Waters, Michigan, received the Canadian patent for his motor sleigh, or "traineau automobile", and on June 27, 1916, he received the first United States patent for a snow-vehicle using the now recognized format of rear track(s) and front skis. Many individuals later modified Ford Model Ts with the undercarriage replaced by tracks and skis following this design. They were popular for rural mail delivery for a time. The common name for these conversion of cars and small trucks was Snowflyers.