At the time of the civil war slavery was already on its way out. It had ended in Europe as being too expensive and would have ended in the US within a few years. Once the Industrial Revolution occurred, keeping a slave was simply cost prohibitive. They had to be fed, clothed, sheltered. They got tired, some were lazy, some got sick and the slave owner had to take care of them even to pay a doctor to treat them. Machines never got tired, they were never lazy, and never got sick. One man and a machine could do the work of 20 or more slaves.
Historically, the great structures of the past could have been built in a comparably short time with a decent construction crew and modern equipment instead of thousands of slaves. At the time, they didn't have modern equipment but they did have thousands of slaves.
Historically, the great structures of the past could have been built in a comparably short time with a decent construction crew and modern equipment instead of thousands of slaves. At the time, they didn't have modern equipment but they did have thousands of slaves.