William McKinley Keller (1901-1974) was a railroad engineer and executive who worked for the Pennsylvania Railroad and the Association of American Railroads.

Keller was born August 29, 1901 in Pittsburg, Pennsylvania to Charles Henry Keller (1857-1936) and Anna McCourtney Keller (1861-1942). He attended public schools in Pittsburgh and Hollidaysburg, Pennsylvania, studied engineering at the University of Pittsburgh, and received a diploma in mechanical engineering from Pennsylvania State College (later Pennsylvania State University).

He entered the railroad industry in 1919 as an apprentice to the Altoona Works of the Pennsylvania Railroad. By 1940, he had advanced through several inspector posts in the test department and to the position of assistant engineer in that department. Keller moved to Philadelphia in 1941 and was made foreman of mechanical engineers; then general forman of car design in 1944; and assistant mechanical engineer in charge of the entire system in 1945.

In 1952, Keller joined the Association of American Railroads (a central coordinating and research agency), in Chicago, Illinois, as director of mechanical research. He became executive vice chairman and director of research of the mechanical division in 1955 and, in 1957, became assistant vice president of the operations and maintenance department. His final position with association was as vice president for research. In this capacity he directed the AAR Research Center on the campus of the Illinois Institute of Technology in Chicago until his retirement in 1968. He also made many public appearances, and took part in four AAR government-sponsored trips to foreign countries: to Russia in 1960 and 1966, to France in 1960, and to Japan in 1964.

After retiring from AAR, Keller served as an independent consultant to the industry and as consulting editor for Progressive Railroading magazine from 1968 to 1974.

He held twelve patents and wrote sixty articles and papers. He was recognized internationally for his achievements in railroad engineering and research. In his early years he made numerous improvements in steam locomotive design, and following World War II, he was largely responsible for developing the design of the lightweight passenger car. He is credited with improved design for truck and freight equipment, automatic car identification, and rail-flaw detection techniques. He also made major contributions in the hot-box field. Technological data provided by Keller were used in modernizing work rules. In 1965, the American Society of Mechanical Engineers bestowed its highest honor (honorary member) on Keller.

Keller died in August 1974 in Overbrook, Pennsylvania.