The Sports Car Club of America (SCCA) is the most active grassroot motorsport organization in the United States. They are a non-profit organization with over 60,000 members participating in 2,000 amateur and professional events each year. The business of events is largely run by the 110 regional chapters united under the wire wheel logo. The national office of the SCCA handles rules, licensing, insurance, and member benefits. They also public the monthly Sports Car magazine, filled with coverage of events and rules addenda. The national office is run by a 13-member Board of Directors and a President (currently Steve Johnson).
The basis of SCCA amateur racing is the Club Racing program. This is road racing with true race cars of all types. Drivers must complete two driver's schools and two regional events before becoming officially licensed. After four regional events, a driver may apply to receive a national competition license. Club racers dream of an invitation to the SCCA National Championship Runoffs®, the Olympics of Club Racing. Don't call them, they'll call you.
The SCCA also hosts a variety of rally events. The most common and accessible is rallycross, an entry-level rally event on a compact course. Road Rally is tamer, but closer to real rally competition. It takes place on paved roadways, but scores drivers based on precision. Getting to the checkpoint late is a penalty, but getting there early is just as large a penalty. Club Rally is next, run by amateur drivers in "normal" cars, but using full-fledged rally stages for competition. Pro Rally is the top of the pile, with full-fledged rally cars racing for days in events across the country. Gran Turismo players will have fond memories of the Suzuki Escudo Pikes Peak, built specifically to compete in the Pro Rally Pike's Peak International Hill Climb.
Solo is undoubtably the most common of the SCCA's sporting events. It is estimated that, aside from drag racing, more Americans compete in Solo 2 (or autocross) events than in any other automotive competition. These events take place in parking lots across the country, as drivers take timed runs at a course marked out by pylons. Pro Solo is similar, but features mirror-image courses. With a single driver on each course, a christmas tree starting light is used to pit the drivers head-to-head. Solo 1 are essentially road races run one driver at a time. Including hill climbs and time trials, these events take place on real competition courses, but without the added risk of several cars racing at once.
Last, but definitely not least, the SCCA organizes Pro Racing series. These are the largest professional road races in the United States. They include the Trans-Am series, which is approaching its 40th anniversary, the SPEED World Challenge, and the newly-formed Formula D drift series.