He was referencing the Bible with “four score and seven years ago”,,, The our fathers meaning Jefferson and Madison and Hamilton establishing our government and explaining how we came together to fight the British. The Gettysburg was pretty much a pep talk for the civil war, so he wanted to express the ideal we had when establishing america, for the good of the people.
There were many things that led to the growth of the Roman Empire, but the best option from the list would be "The Romans were tolerant <span>of most religions of conquered peoples."</span>