Sumo is 2,000 years old. Many consider it the national sport of Japan (despite the fact that besu boru - baseball - is seen by more people) and the wrestlers even have their own cards, just like the baseball players.
It became a professional sport during the early 17th century, at the same time kabuki, bunraku, and ukiyo-e were becoming popular forms of entertainment. The sport has a national governing body, and 70 officially recognized winning techniques. It is not true that the wrestlers simply push each other. Actually, they are skilled athletes, with enormous strength and remarkable agility and quickness for such big men. They average 6' and 325 pounds.
There is much fascinating ritual associated with a sumo bout, from the tossing of salt into the ring as a "purification," to the ritualistic spreading of the arms to show that there are no hidden weapons.
Today, there are two "stables" of wrestlers, the East and the West. These are groups of wrestlers who all train together under the same manager, who rules over them with absolute authority. The wrestlers are paid a salary, and earn extra money during the tournaments when they win a bout.
There are six major tournaments held annually, each lasting 15 days. The wrestlers are carefully ranked, based on performance, and they may be demoted after a tournament for poor performance just as they may be promoted for doing well. However, to become a yokozuna - or grand champion - the wrestler must win three of the six annual major tournaments in a row.
Today, there are two yokozuna, Takanohana and Akebono. Akebono is unusual in that he is an Amerian, born in Hawaii, and one of only a handful of non-Japanese in the sport.