Although Paul MacClintock was only a member of the Illinois State Geological Survey's staff from 1921 to 1928, he produced several publications of pre-Illinoian sediments in Illinois that are insightful and still useful to this day. In 1930, he coauthored a seminal paper with M.M. Leighton on the nature of weathered zones of drift sheets in Illinois.
Born in Aurora, New York, Paul was active in numerous organizations as an undergraduate at the University of Chicago and thrived in the University's invigorating scholarly environment, particularly in Quaternary geology, where he earned a B.S. in 1912. During World War I, he became a lieutenant in the map-making division of the U.S. Army Corps of Engineers. After the war, he returned to the University of Chicago where he received his Ph.D. in 1920; his dissertation was on the Pleistocene history of the lower Wisconsin Valley. He became an instructor, assistant professor, and then associate professor at the University while also working at the Illinois State Geological Survey.
In 1928, Paul accepted the Knox Taylor Professorship of Geography in the Department of Geology at Princeton University, where he spent 30 years before retiring in 1959. After retirement, he was a member of the Vermont Geological Survey from 1960 to 1965 and continued active field research until his final illness.
Professionally, Paul contributed significantly to the development of Quaternary geology in the United States. In addition to some 20 major papers, he was co-editor of two famous textbooks of geology and coauthor of two volumes dealing with the Pleistocene geology of Vermont and the St. Lawrence Lowland. He was a painstaking worker and had great scientific impact through his stimulating expositions and questions in the field, including numerous annual meetings of the Friends of the Pleistocene. According to a memorial resolution that was passed at the Princeton Faculty Meeting in 1970, "Students were perhaps his favorite people. They found him easily accessible, always sympathetic, and sincerely understanding."
Paul also wrote poems that ranged from the puckish to those expressive of his friendliness, gentleness, and warmth to the final journey beyond "the borderland of thought."