Every summer from 1889 until 1910, and in 1920 and 1921, the Divinity School sponsored a special course of study for clergy and other "students of religion." Lasting about two and one half weeks, the participants attended lectures given by the Harvard faculty and other scholars. Those who came from other schools to lecture included Williston Walker from Yale, Arthur McGiffert from Union, Shailer Mathews from the University of Chicago, William Kerby from Catholic University, George H. Coe from Northwestern, Booker T. Washington from Tuskegee, and Solomon Schechter from the Jewish Theological Seminary. In addition to the Divinity School faculty, other Harvard faculty including George Santayana, William James, and Hugo Münsterberg also lectured. President Charles W. Eliot lectured on several occasions. At the end of his presidency in 1909, he delivered a lecture entitled "The New Religion" that aroused strong reaction. Printed in the Harvard Theological Review and as a separate volume, The Religion of the Future predicted that twentieth-century religion would not be bound by dogma or creed.
In the first year, the lectures in the Summer School were on Old Testament, church history, and theology. In 1900, there were lectures in New Testament, history of religions, and homiletics. Afterwards each summer was devoted to a particular topic:
- 1901 The Relation of Ministers to Social Questions
- 1902 Current Problems in Theology
- 1903 Principles of Education in the Work of the Church
- 1904 Contributions to Historical Theology
- 1904 The Bible
- 1906 Christian Theology in its Origin and Development
- 1907 The Relation of the Ministry to Social Ethics
- 1908 The Relation of Christianity to Other Religions
- 1909 Present Religious Conditions and Prospects
- 1910 The Parish Minister
The sessions in 1920 and 1921 included a wide variety of topics.
Most who attended were clergy (for the most part Congregational, Unitarian, Episcopalian, and Universalist). The students came from all parts of the United States and abroad, including Japan and India. In the first year there were 105 students, of whom nine were women. Beginning in 1905, the catalogue of the summer school specifically states "The Summer School is open to men and women alike" (italics original).
Among those who attended in the 1901 session was Margaret Bowers Barnard. Born in 1860 in Bucksport, Maine, and raised in New Orleans, she attended the Carnatz Institute there. When her family returned to New England, she moved to Chelsea and taught French at the Chauncy Hall and Berkeley Schools in Boston. Desiring to study for the ministry, she turned to Dean Everett for help. He assigned a Harvard tutor, Willard Reed, to go to her home in Chelsea once a week; Reed and her minister in Chelsea, Augustus Reccord, referred to this arrangement as "The Chelsea Divinity School." Ordained in 1897, she served Unitarian churches in Rowe and Bernardston, Massachusetts, and did missionary work in the Swansboro, North Carolina, circuit, until her retirement in 1930. She died in 1950.