Answer
Sandra Day O'Connor was the first woman to be appointed to the Supreme Court, serving from 1981 to 2006. She was followed by Ruth Bader Ginsburg, who was appointed in 1993 and continues to serve on the Court. Sonia Sotomayor was appointed in 2009, and Elena Kagan was appointed in 2010. So Kagan is the fourth woman to become a member of the Court.