What is the primary reason the south and the west have increased in population in recent years

The south has been increasing population because of older cities starting to really grow and the fact that factories are starting to become more and more common there, the far west is growing due to an invaluable access to water, which yet again applies to some of the south having access to the Gulf of Mexico, and the Midwest is growing due to the mass amount of untouched land being taken up to become major cities.