Momsen was born in St. Louis, Missouri to Collette and Michael Momsen and lives in Potomac, Maryland where she attended Herbert Hoover Middle School and Winston Churchill High School.[1][3] Her younger sister Sloane Momsen is also an actress. She attended Our Lady of Lourdes Catholic Grade School in University City. She also attended COCA in St. Louis where she took dance classes as a child. She stands at 5'8.She began acting professionally at age three, with a national commercial for Shake 'N' Bake. Then she got a role in The Prophet's Game. In 2000 Momsen got the role of Cindy Lou Who in How the Grinch Stole Christmas. Two years later she got parts in two more motion pictures: Hansel & Gretel, in which she played Gretel, and Spy Kids 2: Island of Lost Dreams, in which she played Alexandra, the President's daughter.
