Willis Appleford Slater was born in the town of Polo, Illinois, on October 14, 1878. At the age of 19, he attended Valparaiso University at Valparaiso, Indiana for two years. Two years later in 1906 Slater furthered his studies at the University of Illinois at Urbana, Illinois, graduating with a Bachelor of Science in Municipal and Sanitary Engineering. Following his graduation, Slater married Clara Mary Knodle and also became a Research Fellow in the Engineering Experiment Station in 1908. Deciding to specialize in reinforced concrete, he graduated with a Master of Science in Theoretical and Applied Mechanics in 1910, also from the University of Illinois. He later received the professional degree of Civil Engineer in 1912 in recognition of his research, and stayed at the University of Illinois, becoming a Research Assistant Professor in 1915. At the onset of the First World War, Slater was called by the Bureau of Standards to serve as an Engineer Physicist, creating reinforced concrete ships for the Emergency Fleet Corporation. The research gained in this project was presented to the American Concrete Institute in 1919 and Slater was awarded the Wason Medal of the Institute in 1920. After the war, he stayed with the Bureau of Standards until 1928, when he took the position of Research Professor of Engineering Materials and Director of Fritz Engineering Laboratory at Lehigh University. In 1929, he was elected vice president of the Lehigh Valley section of the American Society of Civil Engineers. Later that year, he died on October 5, 1931.