Perryville's Merritt "Mickey" McMullen began his softball career in 1954, playing fast pitch before enlisting in the U.S. Marine Corps in 1957. He returned in 1960 and played both fast pitch and baseball in the Baltimore Major League until 1985.
In 1962, he began playing slow pitch, for the Fisherman's Inn and White Horse Hotel. He was known as a slick fielding shortstop and a line drive hitter with occasional power. He joined AA&W in 1964 and played in the Unlimited League at the Marylander in Aberdeen. In 1970, AA&W won the ASA State Tournament; McMullen was the tournament MVP. In the championship game of the ASA Regionals he hit a two-out, 7th inning home run off Fulford TV's Byron Ziegler to tie the game and force extra innings.
In 1968, McMullen was named to the Civilian Welfare Council at Aberdeen Proving Ground and commissioner at the Marylander. Until stepping down in 1980, he ran all of the leagues and tournaments while making many improvements. McMullen transformed the Marylander into one of the premier slow pitch softball meccas on the East Coast, hosting some of the top teams and best competition in the country.