Don Sutton achieved his 300th MLB win on June 18, 1986.
June 18, 1986 - California's Don Sutton becomes the 19th pitcher in ML history to win 300 games, beating the Rangers 3-1 on a three-hitter.
After the game he stated:
"It was hard to remain unemotional. That was the nicest, sweetest roar I've ever heard."
19 Jun 1986, Thu The Vincennes Sun-Commercial (Vincennes, Indiana) Newspapers.com