A uniquely American sport comes to town this weekend -- the rodeo.

Cheyenne may boast of Frontier Days ("The Daddy of 'Em All"), and Houston may have a Livestock Show and Rodeo spread over 25 acres at the Astrodome, but the Washington area has its own Annual Spring Championship Rodeo, now in its second season at Frying Pan Park in Herndon.

Some of the best riders east of the Mississippi will be among the 200 cowboys and cowgirls scheduled to take part in the three- day competition, according to Miriam Kochensparger of the Fairfax County Park Authority. They'll vie for cash prizes and points in the national professional rodeo rankings in seven traditional events: bull riding, saddle bronc riding, bareback bronc riding, women's barrel racing, steer wrestling, calf roping, and team roping.

Featured among the non-competitive performers is 13-year-old Kevin Staples of Dumfries, a trick roper who recently demonstrated his skill on TV's "That's Incredible." Rodeo clowns Bobby Paul and Archie Bunker combine humor and heroics as they distract raging bulls from unseated riders.

Natives of Wyoming and Texas may snicker that the producer of the show, the Triple K Rodeo Company, is based in Hagerstown, Maryland. But Kenny Brown's group has been in business for 16 years and puts on 30 or so shows a year.

Rodeo itself has been around since the mid-1800s, when cowboys, after weeks of trailing cattle from the rangelands to railheads, relaxed by showing off their job skills to a jury of persnickety peers. Tickets were sold to local townsfolk in 1875; today rodeos take place in more than 600 cities and towns throughout the U.S.

Contemporary rodeoing is big business. The 1982 Professional Rodeo Cowboys Association champion "All Around Cowboy," a Californian named Chris Lybbert, roped in more than $120,000 in winnings last year.

For the benefit of those whose closest contact with cowboys (show biz or otherwise) comes while ordering a Double-R-Barburger at a Roy Rogers restaurant, here are a few notes on the various events. BULL RIDING -- This exercise has absolutely nothing to do with raising cattle. It is, however, the most dangerous of all the rodeo competitions. Using only a length of rope held around the bull in a one-handed grip, the rider must remain on board for eight seconds, with his free hand touching nothing but air. Spurring, though not mandatory, gains extra points if done well. Being bucked off or touching the animal with the free hand results in disqualification. SADDLE BRONC RIDING -- Harking back to the ancient art of breaking horses, saddle bronc riding is one of the oldest of rodeo events. Horse and rider are scored separately -- the horse for how hard he bucks, and the rider for his spurring technique -- and the results combined. The rider must spur the horse out of the chute, keep both feet in the stirrups and have his hand on the single rein when the eight-second ride ends. He's disqualified if he changes hands or touches horse, rein or saddle with his free hand. BAREBACK BRONC RIDING -- The contestant attempts to remain astride his mount with the aid of regulation "rigging" -- a leather strap wrapped around the horse's middle and equipped with a grip like a suitcase handle. Spurring must be done only over the break of the animal's shoulders while the cowboy leans back from the handhold. The rest of saddle bronc-riding rules apply. WOMEN'S BARREL RACING -- In this timed event, horse and rider must cover a predetermined course around three barrels. Breakneck speed and low tight turns are mandatory to win. The barrels may be touched, but a five-second penalty is added to the rider's time if one is knocked over. Failure to follow the prescribed pattern results in disqualification. STEER WRESTLING -- The key to steer wrestling, also known as bulldogging, is precision teamwork between the "dogger" who throws the steer and his "hazer" who keeps the quarry running straight. The dogger must leap from his horse and bring the steer to a full halt before throwing it to the ground. The clock is stopped when the steer lies flat on its side with all four feet pointing in the same direction as its head. A world-class dogger can do it in less than four seconds. CALF ROPING -- Here again, teamwork is important, this time between horse and rider. This event comes straight off the ranch; a horse that works with cattle is both bred and highly trained for his job. The horse must close in on the calf and hold a steady distance from it to enable the cowboy to use his rope most efficiently. Once the calf is lassoed, the horse must keep the rope taut while the man throws the animal and binds together any three of its legs with a "piggin' string." The clock stops when the calf is tied. TEAM ROPING -- This event involves two men and two horses. One contestant ropes the steer's horns, and the other its hind legs. The clock is stopped when the ropers, still mounted, face each other with the steer in the dust between them and the ropes secured around the saddle horns. RODEO ROMP The 21/2-hour shows begin at 8 this Friday night; 2 and 8 on Saturday; and 2 on Sunday. Admission is $5, with those two and under admitted free. Tickets are being sold in advance; call 703/437-9101. To reach Frying Pan Park, 2709 West Ox Road, Herndon, take Exit 9W (I-66) off the Beltway to U.S. 50 in Chantilly; turn right onto Centreville Road; right again onto West Ox Road.