Complex sentence: With geographic, social, political, and economic connection to both the North and the South, the border states were critical to the outcome of the war, and still delineate the cultural border that separates the North from the South.
Split into simpler sentences: With geographic, social, political, and economic connections to both the North and the South, the border states were critical to the outcome of the war. They are considered still to delineate the cultural border that separates the North from the South.