In A People's History of the United States by Howard Zinn, what was "the other Civil War"?

Zinn sees
"the other civil war" as the conflict between the rich and poor in mid-nineteenth
century America.

Zinn's "other civil war" is meant to challenge the
conventional thinking about the Civil War that took place in the United States.  Most sources of
American History argue that the Civil War was between slavery in the South and the Northern
desire to abolish it.  Zinn's problem with this retelling is how it fails to adequately explore
the emerging economic division in mid-nineteenth century America. 

Zinn's
"other civil war" is rooted in America's emergence into an industrialized nation.  He
speaks of how the movement from farms to factories, the consolidation of urbanization, and the
rapid rise of technology helped to facilitate the power of the rich over the poor.  Such a shift
advanced the agenda of the wealthy and neglected the needs of everyone else.  Zinn focuses on
different examples of resistance in the mid-nineteenth century that sought to challenge a
structure where...