James Edward Dempsey was born in Providence, Rhode Island, February 22, 1912, the son of Joseph M. Dempsey and Julia Mary McSherry. He attended St. Mary's Grammar School, LaSalle Academy and Providence College in Providence, Rhode Island. In August 1935, he entered the Dominican novitiate at St. Rose of Lima Priory, Springfield, Kentucky, receiving the religious name of Michael, and made his first profession there on August 16, 1936. From 1936 to 1939 he pursued philosophical studies at the Dominican House of Studies, River Forest, Illinois, and made his solemn profession on August 16, 1 939. He elected to join the new Province of St. Albert the Great and so continued his theological studies at the Dominican House of Studies in River Forest, where he was ordained by Bishop Bernard J. Sheil on June 11, 1942.

Having completed his basic studies, Father Dempsey was assigned to Fenwick High School, Oak Park, Illinois, where he taught English and religion from 1943 to 1950. During this time he also attended DePaul University, Chicago, Illinois, and obtained a master's degree in English literature. In 1951 Father Dempsey was asked to undertake foreign mission work in Nigeria, Africa, and was among the first three friars sent by the Province of St. Albert the Great to this new mission territory. From 1951 to 1965 he served as pastor and local superior of St. Dominic's Parish, Yaba, Lagos State. In 1965 he was appointed Vicar Provincial of the Dominican friars in Nigeria and moved to Our Lady of Fatima Church, Gusau, Sokoto State.

On July 13, 1967, Father Dempsey was appointed the second Bishop of Sokoto, Nigeria, and on August 15, 1967, was ordained bishop at St. Pius V Church, Chicago, Illinois, by

Cardinal John P, Cody, Archbishop of Chicago, assisted by Archbishop John Aggey of Lagos, Nigeria, and Bishop Aloysius Wycislo, Auxiliary bishop of Chicago. He was formally installed as ordinary of the diocese on October 1, 1967. Because of failing health as well as his belief that the diocese had need of an indigenous bishop, he submitted his resignation to Pope John Paul II on May 8, 1984. His resignation was formally accepted on December 31, 1985.

Bishop Dempsey returned to the United States in the fall of 1985 and, exercising his privilege of choosing a house of the Order in which to reside, took up residence at St. Dominic Priory, Denver, Colorado, where he spent the last years of his life. There he was active in assisting at St. Dominic Parish, especially in ministry to the sick and aged. Declining health necessitated his move to Mullen Home in Denver, a care facility sponsored by the Little Sisters of the Poor. There he died on the morning of March 19, 1996. A Mass of Christian Burial was celebrated by Archbishop J. Francis Stafford of Denver at St. Dominic's church on March 25, 1996, and Bishop Dempsey was buried in the Dominican plot at Mt. Olivet Cemetery, Denver.