Complex sentence: Madalyn Murray O'Hair (April 13,1919--September 29,1995) was an American atheist activist and founder of the organization American Atheists and its president from 1963 to 1986.
Split into simpler sentences: Madalyn Murray O'Hair (April 13,1919--September 29,1995) was an American atheist activist. She was the founder of the organization American Atheists and served as its president from 1963 to 1986.