Complex sentence: The city is one of the older suburbs in the St. Louis area, having been a streetcar suburb in the late nineteenth and early twentieth centuries; much historic architecture remains in the southern, older portion of the city, particularly along Delmar Boulevard.
Split into simpler sentences: The city is one of the older suburbs in the St. Louis area, having been a streetcar suburb in the late nineteenth and early twentieth centuries. Much of this legacy is reflected in the historic architecture in the southern, older portion of the city, particularly along Delmar Boulevard.