In 1959 four more community pools joined the original six--Bannockburn, Daleview, Wheaton Woods, and Wheaton Haven. (In 1996, Wheaton Haven's pool closed and the team merged with Kenmont.) I'm still quoting the league history:
This  was the first year of the Montgomery County Swim League. These ten pools [yesterday's list and today's] were the Charter Members and Peggy Whilden was elected President on June 20, 1959. A constitution and by-laws were adopted on September 22, 1959 at a meeting held at the Merlands Club. The Second Annual Maryland Metropolitan Area Community Pool Meet scheduled thirty events."