Daniel Craig McCallum was a Scottish-born American railroad engineer, general manager of the New York and Erie Railroad and Union Brevet Major General of the United States Military Railroads during the American Civil War, known as one of the early pioneers of management. He set down a group of general principles of management, and is credited for having developed the first modern organizational chart.

An organizational chart, also called organigram, organogram, or organizational breakdown structure (OBS), is a diagram that shows the structure of an organization and the relationships and relative ranks of its parts and positions/jobs. The term is also used for similar diagrams, for example ones showing the different elements of a field of knowledge or a group of languages.