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The "Father of American Folk Music" has died. 

The New York Times says Pete Seeger passed away Monday at the age of 94.  Seeger's grandson, Kitama Cahill Jackson, says the iconic singer-songwriter and activist died of natural causes at New York Presbyterian Hospital. 

Throughout his lengthy career -- which saw him perform into his 90s -- Seeger served as a champion of folk music with classics like "This Land Is Your Land," "We Shall Overcome," "If I Had a Hammer," and "Turn, Turn, Turn." 

But he was equally known for using that music to help bring about social change.  His many political activities ranged from standing up to Congress and getting convicted for contempt after defying the House Un-American Activities Committee in the 1950s, to lending his voice to civil rights marches in the 1960s.  And in 2009, he stood on the steps of the Lincoln Memorial to sing at the inauguration concert for President Obama.