Differences in regional economic development during the 19th century produced which of these conditions in the united states at the time of the civil war? a the north was the nation's main industrial area. b the south was the main destination for immigrants. c the north was the nation's main cotton-producing area. d the south was the nation's main transportation center for agricultural goods. i know historyguy has already answered this but he isnt the most reliable source so i just want to ask this just in case.