You are probably thinking of the Mississippi river.
What were 5 border states during the civil war
border states
The three border states during the US Civil War were Missouri, Kentucky and Maryland. The were slave states but did not join the Confederacy. Delaware also had slaves and was not "on the border" between the North and the South
The North had 18 715 055 population. The Border States had 3 024 743 population.
Delaware Kentucky Maryland Missouri and west Virginia
34 022 kilometers, to which it should be added that of the Border States of 3 020 kilometers
during civil war south wanted slavery but north was fighting it
Because these four important states could have tilted the war in favour of whoever they supported. In the end, it was the North.
Some did and some went South to join the Confederates, a situation that happened in most border states with divided loyalty.
Kentucky, Missouri, Maryland, Delaware
It was strictly forbidden to. But quite a lot of cross-border trading (both ways) did go on, especially in the West.
The three principle products of the North during the Civil War were, textiles, lumber, and clothing.