Anton Boisen is considered the father of CPE.
He was a Congregational minister in the USA, who during the 1920s and 30s suffered a series of psychotic episodes, for which he received treatment as a patient in a psychiatric hospital.
It was as a direct result of these experiences that Boisen conceived the idea of grounding the pastoral formation of theological students in the reality of the hospital setting, of ‘hands-on’ pastoral care. And so he invited students to minister within the hospital, and then to reflect with him and their peers on their experiences.
Thus was CPE born; and it has grown from that small beginning to the international program it has since become.
Other resources on the history of CPE:
You can find a slightly extended version of the Boisen story on the website of the Association for CPE (USA). This article also expands the story to acknowledge the role of Richard Cabot, Helen Dunbar and others in the Boisen story, and then provides information on the development of CPE.
Wikipedia also has an article on Boisen’s life.
For an introduction to CPE within the Australian context, refer to Joan Kenny’s book A finger pointing to the moon (John Garratt Publishing, Mulgrave. Vic). This work focuses on CPE in Victoria, but provides valuable information for the wider Australian CPE scene.