The Fourth Migration consisted of

A.
Midwesterners.

B.
Southerners.

C.
Californians.

D.
Mexican workers many of whom were undocumented.

Ifound this on google “simply, the working conditions were terrible during the industrial revolution. as factories were being built, businesses were in need of workers. with a long line of people willing to work, employers could set wages as low as they wanted because people were willing to do work as long as they got paid.” i hope this you for what your looking for.