The demographics of immigration meant that the North was pulling steadily ahead of the South in the House of Representatives by the time of the Mexican-American War. This alarmed the slave-holding states and made them more determined than ever to maintain a “balance” in the US Senate. read more
Given the trajectory the South had taken plus the problems arising from the Compromise of 1850 at the end of the Mexican-American War and, later, the Kansas-Nebraska Act with all the resulting violence, I tend to disagree with the other posters and say it really was unavoidable. read more
Actually, what we ended up with following the war – 100 years of apartheid, segregation and Jim Crow laws – is probably what would had to have been agreed to in order to avoid the Civil War. read more