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United States' Michael Phelps waves after finishing first in the men's 200-meter butterfly swimming semifinal at the Aquatics Centre in the Olympic Park during the 2012 Summer Olympics in London, Monday, July 30, 2012. (AP Photo/Daniel Ochoa De Olza)

Phelps makes Olympic history

Michael Phelps became the most decorated Olympian of all time after

winning his 18th gold medal in the 4x100m medley relay at the London Aquatics Centre on Aug. 4, finishing his career with a staggering 22 medals and the title of greatest Olympic athlete in history.