Robert Almer Harper, botanist, was born in Le Claire, Iowa, on January 21, 1862. After earning his bachelor's degree at Oberlin College in 1886, Harper taught at Gates College (1886-1888) and Lake Forest Academy (1888-1891). He earned his M. A. from Oberlin in 1891 and was appointed professor of botany at Lake Forest College. From 1894 to 1896, Harper took a sabbatical from teaching to pursue his doctoral degree in Germany, studying with Strasburger Brefeld. In 1898, he was appointed professor and head of botany at the University of Wisconsin, a position he would hold until 1911, when he was appointed head of the botany department at Columbia University.

During the 1920s, Harper also served as chief of the board of scientific directors of the New York Botanical Garden. He belonged to a number of scientific organizations, including the National Academy of Sciences, the American Academy of Arts and Sciences, the American Philosophical Society and the Botanical Society of America.

Harper married twice: first, in 1899, to Alice Jean McQueen (died 1909); and to Helen Sherman (1879-1973) in 1918. He retired in 1930, moving to Bedford, Virginia, where he died on May 12, 1946.