Complex sentence: This film was largely shot in the vicinity of El Reno, Oklahoma, using the facilities of what was at the time the Rock Island railroad (now Union Pacific), though some of the moving background shots show East Coast scenes such as bridges.
Split into simpler sentences: This film was largely shot in the vicinity of El Reno, Oklahoma. It used the facilities of what was at the time the Rock Island railroad (now Union Pacific), though some of the moving background shots show East Coast scenes such as bridges.