Sunday marked the fortieth anniversary of the Stonewall riots, which began when patrons of a Greenwich Village gay bar fought back against a police raid. Though gay civil rights activism wasn't new, the events at Stonewall Inn are credited with catalyzing the development of an organized gay pride movement.

Click through to learn more about the Stonewall riots and how they are being remembered in 2009.

--Elise Foley

Courtesy of Columbia University and Getty Images