On this day in 2004, 40-year-old Arizona Diamondbacks lefthander Randy Johnson becomes the oldest pitcher in major league history to throw a perfect game, leading his team to a 2-0 victory over the Atlanta Braves. A “perfect game” is when a pitcher faces a minimum 27 batters, recording 27 outs. Through the 2006 season, only 17 perfect games had been thrown, including 15 in the modern era (post-1900).

Johnson, known for his overpowering fastball, struck out 13 batters in the game. He led the National League in strikeouts for the fifth time that year; he had previously won four strikeout titles in the American League, even though managers routinely stacked their lineups with right-handed hitters to combat Johnson’s utter dominance of left-handers. The 6-foot-10-inch “Big Unit” used his height and length to full advantage, striding towards the plate and throwing the ball sidearm, so that left-handers could not see the pitch until it was on top of them or past them.

Johnson had already thrown a no-hitter in 1990 for the Seattle Mariners; he missed a perfect game that day by walking seven batters. In 1995, still with Seattle, he won his first of five Cy Young Awards, given each year to the best American League and National League pitchers. His next four Cy Youngs came consecutively from 1999 to 2002, while he pitched for the National League’s Arizona Diamondbacks. In 2001, Johnson set a major league record with an average of 13.41 strikeouts per nine innings. He was also the fifth player to throw no-hitters in both the American League and National League after Cy Young, Jim Bunning, Nolan Ryan and Hideo Nomo.

The oldest pitcher to throw a no-hitter in the major leagues was 44-year-old Texas Ranger Nolan Ryan in 1991. It was the seventh no-hitter of Ryan’s career. He never threw a perfect game.