On July 15, 1936, the Mercury, Michigan’s first streamlined passenger train began service on the New York Central System between Detroit and Cleveland. By November 1938, the Mercury was also operating between Detroit and Chicago.
Two train sets serviced these trains, but the schedule was such that one train set began the day in Cleveland, ran to Detroit as the Cleveland Mercury, and ran from Detroit to Chicago as the Chicago Mercury, while the other set did the reverse run (the eastbound Chicago Mercury arrived in Detroit after its westbound counterpart had left, so the NYC would have needed an extra train set, if it had not shared sets across trains). The Cleveland run was on a 2:50 hour schedule and the Chicago run took 4:45.
Mercury Train wikipedia entry which cites :
Cook, Richard J. Sr. (1991). The New York Central’s Mercury: The Train of Tomorrow. TLC Publishing; Lynchburg, VA, pp.6-9