Bush, a graduate of Stevens Institute of Technology, had worked his way up from apprentice mechanic at the locally based Pittsburgh, Cincinnati, Chicago and St. Louis Railroad to superintendent of motive power at that railroad, and, briefly, the Milwaukee Road. In 1908, Rockefeller departed, and Bush took over as president, a job he would hold until 1928.
Bush's career trajectory involved his progression from an apprentice mechanic to superintendent of motive power at the Pittsburgh, Cincinnati, Chicago and St. Louis Railroad, followed by a brief stint as president of the Milwaukee Road. After Rockefeller left in 1908, Bush assumed the presidency of the company, which he held until 1928.