actual reasons:

1) the south was originally the states below the mason-dixon line, characterized by lots of slavery, agriculture, a small wealthy elite and a ton of poor people. contrast with the north which was industrial, cosmopolitan, had more socioeconomic classes, and was less keen on slavery.

2) california was admitted to the union as a free state, thus no slaves even though it has a ton of agriculture.

3) because of 2, CA did not have the same politics or populace as the South, and also didn't secede from the Union

4) AZ and NM are also not 'the South' because they were territories at the time and only saw some minor skirmishes, in addition to not having slavery related politics. UT, CO, and NV were also not involved, even though all are south of the mason-dixon line.