The Washington High School league began in 1987 with three teams: Bainbridge Island, Greenwood Club, and Lakeside. A few years later Bellevue High School joined the league to add a bit more variety to the schedule. Overlake School and Forest Ridge were added as varsity teams in 1993, and Holy Names Academy in1995, Kitsap  in 1996. 

All varsity teams added after Bellevue were allowed a "breaking-in" period for a couple years and played at the JV level first. In 1997 the varsity league grew to 11 teams as Forest Ridge, Lake Washington (Eastside), Mercer Island, and Vashon all moved up from the JV division. In 1999 the league had a record 18 teams (10 varsity, 8 JV) fed by six middle school teams. The growth of youth lacrosse in the Northwest parallels its growth across the country. In recent years, several of our Washington players have received National recognition as All-Americans and are playing on D1 college teams. Additionally each year since 1995, the Northwest Region has sent a select team to compete at the National Tournament on the east coast.  Each year shows significant strides in the level of competitiveness that our northwest girls display against the east coast teams which as a whole field players who started their lax careers at a much earlier age.

In 2002 the league's name was changed from Northwest Schoolgirls to Washington Schoolgirls' Lacrosse Association (WSLA) and formed two varsity divisions. the A division has six teams and the B division has seven teams. The JV league has eleven teams, and there are eight youth teams.  Fourteen organizations carry a total of 32 teams for an astounding 88% increase in the past three years.