Theologian and author of Serenity Prayer who greatly influenced both political thought and Protestantism in America.
He was ordained a pastor in 1915, taking over a small church in Detroit and growing it from 46 to over 700 members over the course of a decade.
Charting his own philosophical course, he contradicted both liberals in their views on the Social Gospel and religious conservatives in their views on biblical realism.
His wife Ursula Niebuhr founded the Department of Religion at Barnard College.
His idealogical legacy influenced everybody from Martin Luther King to Vietnam War policymakers to Barack Obama.