The first women's lacrosse game was played in 1890 at the St. Leonard’s School in Scotland.  Although an attempt was made to start women's lacrosse at Sweet Briar College in Virginia in 1914, it was not until 1926 that Miss Rosabelle Sinclair established the first women's lacrosse team in the United States at the Bryn Mawr School in Baltimore, Maryland.

Men's and women's lacrosse were played under virtually the same rules, with no protective equipment, until the mid-1930s. At that time, men's lacrosse began evolving dramatically, while women's lacrosse continued to remain true to the game's original rules. Men's and women's lacrosse remain derivations of the same game today, but are played under different rules. Women's rules limit stick contact, prohibit body contact and, therefore, require little protective equipment. Men's lacrosse rules allow some degree of stick and body contact, although violence is neither condoned nor allowed.

Excerpt from US Lacrosse Web site. 
http://www.uslacrosse.org/the_sport/index.phtml

Learn more about the rules!
http://www.uslacrosse.org/womens_div/pdf/womens2008RuleBook.pdf