Robert L. Slagle left a position as President of the South Dakota School of Mines to become president of South Dakota Agricultural College, as it was then known. As an educator accustomed to South Dakota and the political climate of higher education, Slagle was able to weather many financial difficulties and have a lasting effect on both the school and the state. Stricter standards made it necessary for students to complete four years of high school before entering a degree program. Slagle also oversaw the reorganization of agricultural courses, the establishment of a summer, and many buildings, including Wenona Hall, were built. The tradition of Homecoming began in 1908, and the first Hobo Day at State took place in 1912.
One of the most visible modifications Slagle implemented was to change the name of the institution. The new name, South Dakota State College of Agricultural and Mechanical Arts, reflected not only the general coursework and agricultural classes taught, but also the engineering discipline. The new name was retained until the college became a university in 1964.
Other notable changes during Slagle's tenure included the implementation of the Summer School and correspondence courses which helped almost double enrollment. Slagle also started the School of Agriculture that existed at the college until 1961. This innovative school offered high school courses during the five winter months, making secondary education a possibility for a large number of rural students.
Slagle moved on to a position at the University of South Dakota.