I have noticed that during the years before the civil war the US is often referred to as the Union. This trend continues on through civil war and for some time afterward. Why was it referred to like this and when did it stop being referred to as the union?
In his first inaugural address, Lincoln used "the Union" twenty times. After three years of civil war, the Gettysburg Address did not have one mention of "union" but instead said "nation."
Prior to the Civil War, Americans preferred "union" because it implied that the federation was voluntary. When states actually tried to leave, Lincoln and others switched to "Nation" to try to unite the country more.