Ted Williams hit .406 for the entire 1941 season. He is the last Major League player to hit .400 for a whole year.
From the start of baseball’s modern era (1900) until Bill Terry hit .401 in 1930, there were 11 occurrences of a player hitting .400 or more. Williams was the first and last .400 hitter after Terry.
After Williams’s Red Sox lost to the Indians on May 16, 1941, he was hitting a perfectly respectable .333, but between the May 17 and May 25, he went 19 for 39, and lifted his average to .404. Williams was hitting above .400 for the entire month of June, but he hit a “soft spell” at the beginning of July, and by July 19 his average was down to .393. That was his low point for the remainder of the the season. He was hitting exactly .400 on July 25, and he never got below that level for the rest of the way.
After a 3 for 5 game on September 7, Williams’s average spiked to .413, and he appeared to be cruising to a .400 season, but going into the last day Williams had slid back to .400 again.
The 1941 season ended with the Red Sox playing the A’s in a doubleheader at Shibe Park (later renamed Connie Mack Stadium) in Philadelphia. At that point in the season the Red Sox were in second place, but the Yankees had long since run away with the American League Pennant and had a 17 game lead over Boston. For what little it was worth, the Red Sox’ second place finish was also a done deal. Chicago was seven games behind them in third place. And the A’s certainly weren’t going anywhere. They were in dead last place, seven games behind the seventh place Washington Senators.
Williams’ actual batting average before the final double header was 0.399553571428571, which of course rounds to .400.
It’s doubtful that anybody would have cared if Williams sat out the whole double header in order to secure his .400 average, but “Teddy Ballgame” wouldn’t have any parts of that.
He went 4-5 in the opener (three singles and a home run, and two RBIs). That took his average up to .404. As long as Williams didn’t go 0-6 in the second game, he was going to be a .400 hitter. As it turned out, he went 2-3 and wound up the season hitting 0.405701754, or was we say four-oh-six!