The Rumba was originally a marriage dance. Many of its movements and actions which seem to have an erotic meaning are merely depictions of simple farm tasks. Rumba became a popular ballroom dance and was introduced in the United States about 1933. Rumba was at the beginning of the Cuban and American dance crazes, and was the basis for the Mambo, and the Cha Cha. Rumba is usually written in 4/4 time. The characteristic feature is to take each step without initially placing the weight on that step. Steps are made with a slightly bent knee which, when straightened, causes the hips to sway from side to side in what has come to be known as "Cuban Motion".