Hartley H. T. Jackson (1881-1976) was a native of Milton, Wisconsin where he started his studies in zoology at age 11. In his early years he became acquainted with Ludwig Kumlien, later his college teacher, and Ned Hollister, then a Wisconsin naturalist. Following his graduation in 1904 from Milton College he taught science in Missouri, Wisconsin and Illinois before taking a graduate scholarship at the University of Wisconsin, where he received his Master's degree in 1909. While at Wisconsin, Jackson taught laboratory zoology and identified, arranged and catalogued the Department's bird collection. During the summers he worked with the Wisconsin Geological and Natural History Survey.
In 1910, the Bureau of Biological Survey offered Jackson a position on its research staff, and he was placed in charge of the Bureau's mammal collection. In 1924 he became chief of the Division of Biological Investigations and in 1936 was placed in charge of the Section of Wildlife Surveys, later Biological Surveys. He remained in that position until 1951 when the Section was merged with that of Distribution and Migration of Birds, and he became mammalogist in the new Section of Distribution of Birds and Mammals.
Jackson was one of the founders of the American Society of Mammalogists and served as chairman of its organizing committee in 1919. He has also served the Society as corresponding secretary, 1919-25; editor of the Journal of Mammalogy, 1925-1929; and president; 1938-1940.
His primary research interests were the mammalogy of his native state, the life zone concept of Clinton Hart Merriam, and the taxonomy of mammals and mammal distribution. He published extensively, his major work being the Mammals of Wisconsin, 1961.