Complex sentence: His regular fireman on No.638 was his close friend, John Wesley McKinnie, with whom he worked exclusively from about 1897 until he went to the passenger run out of Memphis with his next and last fireman, Simeon T. "Sim" Webb in 1900.
Split into simpler sentences: His regular fireman on No.638 was his close friend, John Wesley McKinnie, with whom he worked exclusively from about 1897 until he went to the passenger run out of Memphis. There he worked with his next and last fireman, Simeon T. "Sim" Webb in 1900.