At Kansas City in the second game of a doubleheader, Cleveland’s 43-year-old Early Wynn leaves with a lead after struggling through five innings. Four scoreless relief innings by Jerry Walker enable Wynn to score his 300th career victory, 7 – 4. It has taken Wynn eight tries to cop his 300th (and last) career win.

On July 13, 1963At Kansas City in the second game of a doubleheader, Cleveland’s 43-year-old Early Wynn leaves with a lead after struggling through five innings. Four scoreless relief innings by Jerry Walker enable Wynn to score his 300th career victory, 7 – 4. It has taken Wynn eight tries to cop his 300th (and last) career win.

Source
Baseball Reference July 13