Question: when did central pacific railroad trains first pass over donner summit
Answer: Clement ( 1837 -- 1914 ) , the original ( Track 1 ) summit grade remained in daily use from June 18 , 1868 , when the first CPRR passenger train ran through the Summit Tunnel , until 1993 when the Southern Pacific Railroad ( SP ) ( which operated the CPRR - built Oakland - Ogden line until its 1996 merger with the Union Pacific Railroad ( UP ) ) abandoned the 6.