Bixby, Jerome. "One Way Street"
Summary: A physics experiment knocks a passerby into a similar timeline, and he must be returned to save the universe. Numerous small things are changed (e.g., Shakespeare didn't write Hamlet, the Korean War only lasted two months, etc.), but allohistorical content is negligible.
Published: In Amazing Stories, January 1954; Best Science Fiction Stories and Novels: 1955 (ed. T.E. Dikty), Fredrick Fell 1955; Space by the Tail, Ballantine 1964; and Robert Adams' Book of Alternate Worlds (eds. Robert Adams, Martin H. Greenberg, and Pamela Crippen Adams), q.v.