The North was able to replenish its military in the face of staggering loses on the battlefield by using the steady stream of new immigrants. The Irish would get recruited as soon as they got off the ship in New York.
The main reason why so many of the machines that sped up production and travel were invented during the 18th and 19th centuries is because this was the time of the Industrial Revolution, which saw a great increase in factory production, which helped create the machines in question.
Im sorry i answered but then I got scared