Who resigned from the US Supreme Court in 2009?

Sonia Sotomayor

President Obama nominated Sonia Sotomayor on May 26, 2009, to replace retired Justice David H. Souter. Justice Sotomayor was confirmed by the Senate on August 6, and sworn-in on August 8, 2009. She began sitting with the Court immediately prior to the 2009-2010 Term.

Justice Sotomayor was the third woman appointed to the Supreme Court, and the first Latina justice in the Court's history.