Nouwen developed a strong interest in a cross-disciplinary study of psychology and theology and moved to the United States in 1964 to study at the Menninger Clinic in Topeka, Kansas. While in the United States, he became interested in the civil rights movement and joined Martin Luther King Jr.’s 1968 march from Selma to Montgomery. He also spent two years teaching clinical psychology courses at the University of Notre Dame before returning, in 1968, to the Netherlands, where he worked at the Amsterdam Joint Pastoral Institute and the Catholic Theological Institute of Utrecht.  In 1971 Nouwen again travelled to the United States, this time responding to an invitation to teach at Yale Divinity School. 

In 1974, Nouwen spent seven months living, worshiping, and working alongside the Trappist monks in the Abbey of the Genesee in Piffard, New York. He went on to explore various other groups, teaching positions, and missions in a desire to discover where his calling was leading him. This search included work with Maryknoll missionaries in Peru and Bolivia and led to his involvement with L’Arche, a movement of communities for the disabled. Nouwen eventually moved to L’Arche Daybreak near Toronto, Canada, where he lived for the rest of his life. He died on September 21, 1996 while travelling through his homeland, Holland. During his life Henri Nouwen authored more than forty books, which have sold more than two million copies and been translated into at least twenty languages.