Complex sentence: As the city came to be more and more congested, further means of transportation were sought; eventually leading to horse-drawn trolleys which eventually became electric trolleys that ran down the main streets of downtown Newark including Broad Street and up Market Street near the courthouse.
Split into simpler sentences: As the city came to be more and more congested, further means of transportation were sought, eventually leading to horse-drawn trolleys. These, in turn, were replaced by electric trolleys that ran down the main streets of downtown Newark including Broad Street and up Market Street near the courthouse.