Listed at 5 ft 3 in (1.60 m), 138 lb, Lester batted and threw right-handed.

[2] Mary Louise Lester was one of the original founding members of the All-American Girls Professional Baseball League in its 1943 inaugural season.

[3] In 1943, Lester attended the final tryouts of the league at Wrigley Field.

Once the final cut was made, Lester and another 59 of the 280 girls who tried out were chosen to become the first women to ever play professional baseball.

She was relocated to the Kenosha Comets,[4] playing for them one year before joining the South Bend Blue Sox[5] in the 1944 season.