which technological advancement had the greatest impact on the growth of the U. S. after the civil war and why ?

it's not just about advancement of technology but also for starting wars in Arab an other countries and make money out of it.

lee and grant, both of whom held the highest rank in their respective armies, had known each other slightly during the mexican-american war (1846-48) and began their dialogue by exchanging awkward personal inquiries. characteristically, grant had arrived in his mud-splattered field uniform while lee had turned out in full dress attire, complete with sash and sword.

explanation: