Reuben E. Nelson was an influential leader within the American Baptist Convention (ABC) for three decades. Prior to the beginning of his professional career, Nelson received degrees from several different universities. He received his Bachelor of Arts from Des Moines University in 1927, his Bachelor of Divinity from Bethel Theological Seminary (BTS) in 1930, and his Master's of Sacred Theology from Andover Newton Theological Seminary in 1933. He was married to Edith Catherine Peterson in 1933.

Following his graduation from Bethel, Nelson served as Pastor in Brockton, MA for three years until 1934. He then worked as the Promotional and Educational Secretary at BTS until 1937 when he became a Professor of Biblical Interpretation, also at Bethel. In 1938, Nelson moved to Minnesota and became the Executive Secretary for the ABC there. He served until 1943, at which time he moved to the Detroit Baptist Missionary Society to also serve as Executive Secretary. In 1945, Nelson became the Director of Finance and Promotion. In 1950, the ABC created a new position for Nelson; he became the first General Secretary of the ABC. Nelson suffered a massive heart attack in 1955 but held the position until 1959 when his poor health required him to step down.

During his lime with the ABC, Nelson attended the First and Second Assemblies of the World Council of Churches in 1948 and 1954, the Faith and Order Conference in 1952, and the Baptist World Alliance in 1950. Nelson continually preached and spoke at churches and conferences. He also wrote and was written about in numerous articles. His writings include "Christian Courtesy" from The Ecumenical Review in 1953 and several articles for The Watchmen Examiner.