Complex sentence: In February, 1901 the "Overland" took 74 hours and 15 minutes from Chicago to San Francisco, and by 1920 this was down to 72 hours each way, leaving San Francisco eastbound at 9AM and Chicago westbound at 7:10PM.
Split into simpler sentences: In February, 1901 the "Overland" took 74 hours and 15 minutes from Chicago to San Francisco. In 1920 it took 72 hours each way, leaving San Francisco eastbound at 9AM and Chicago wstbound at 7:10PM.