Complex sentence: In 1953, the last streetcars ran in the city; trolleybuses made "their" final run in the city four years later in 1957, leaving the city with an all-bus transit system.
Split into simpler sentences: In 1953, the last streetcars ran in the city. Trolleybuses made their last run in the city four years later in 1957, leaving the city with an all-bus transit system.