Defending heavyweight champion Muhammad Ali goes down in the ninth round of the title bout against challenger Chuck Wepner, from Bayonne, N.J., at the Richfield Coliseum, in Cleveland, Ohio, on March 24, 1975. Ali tripped over Wepner's foot, but the referee ruled it as a knockdown. Ali later knocked out Wepner in the 15th round to retain his title. (AP Photo)