The 1941 baseball season ended on this day, with Boston's Ted Williams closing the season with a .406 batting average. It's the last time that a player batted .400 over a complete season.
A perennial question is which record is more unbreakable: Williams' .406 average or DiMagio's 56 game hitting streak. Both are subject to Umpires expanding or contracting the strike zone; a hitting streak can be kept alive pretty easily via this. Not so much the batting average.
There's an old story about this. A young pitcher was facing Williams. His first pitch was called a ball, even though he thought he had found the strike zone. The second pitch fared no better. Frustrated, the pitcher complained to the Umpire. The Umpire replied, "Son when it's a strike, Mr. Williams will let you know."