Complex sentence: Much of the open space in Colton has been built upon, making it a much more urban area, and in the mid 1990's, "Colton Retail Park" was opened in the east of the area, now with many well known stores.
Split into simpler sentences: Much of the open space in Colton has been built upon, making it a much more urban area. In the mid 1990's, "Colton Retail Park" was opened in the east of the area, now with many well known stores.