Complex sentence: On December 25,1858 the Pittsburgh, Fort Wayne and Chicago Railroad opened as far as Van Buren Street in Chicago, and it built the first station at what would eventually become today's Union Station on the west bank of the Chicago River.
Split into simpler sentences: On December 25,1858 the Pittsburgh, Fort Wayne and Chicago Railroad opened as far as Van Buren Street in Chicago. It built the first station at what would eventually become today's Union Station on the west bank of the Chicago River.