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 the very few controlled most of American industry and economic production.  Zinn's analysis details Northern agrarian social movements that challenged an unfair economic reality:  "The farmers had fought, been crushed by the law, their struggle diverted into voting, and the system stabilized by enlarging the class of small landowners, leaving the basic structure of rich and poor intact. It was a common sequence in American history."  The "other civil war" was between rich and poor.  It was rooted in the unfair development of American capitalism in the mid-nineteenth century.

The "other civil war" was not merely fought in Northern rural settings.  Zinn details how economic challenge in the Northern urban settings made life increasingly difficult: "In Philadelphia, working-class families lived fifty-five to a tenement, usually one room per family, with no garbage removal, no toilets, no fresh air or water. There was fresh water newly pumped from the Schuylkill River, but it was going to the homes of the rich."  The "other civil war" was fueled by the the growing resentment that poor people had regarding the difficulty of their lives while the rich lived theirs with ease.

In New York you could see the poor lying in the streets with the garbage. There were no sewers in the slums, and filthy water drained into yards and alleys, into the cellars where the poorest of the poor lived, bringing with it a typhoid epidemic in 1837, typhus in 1842. In the cholera epidemic of 1832, the rich fled the city; the poor stayed and died.

Workers in the North could not survive on the incomes factory owners were paying them.  The debilitating effects of economic expansion fueled resentment. Zinn argues that a result of this dissatisfaction was "sporadic reactions from the poor" such as "spontaneous, unorganized uprisings against the rich."  This gulf was the root of "the other civil war."

Zinn makes clear how "the other civil war" was also fought in the Southern part of the United States.  Zinn believes this proves how the belief that slavery was the dividing line between North and South is flawed.   Poor people existed on both sides of the Mason-Dixon line:

Most whites-two-thirds of them-did not own slaves. A few thousand families made up the plantation elite. The Federal Census of 1850 showed that a thousand southern families at the top of the economy received about $50 million a year income, while all the other families, about 660,000, received about $60 million a year.

Zinn argues that a majority of the South consisted of poor farmers, "living in shacks or abandoned outhouses."  Even those who worked in factories found their lives extremely difficult: "A newspaper in North Carolina in August 1855 spoke of "hundreds of thousands of working class families existing upon half-starvation from year to year."  These Southerners did not share much in common with the gentry who owned mammoth plantations.  They had more in common with the farmers and workers challenged under Northern industrialization.  Zinn wants to make clear that the traditional view of the Civil War is an elitist one.  It pits the "planation elite" against their Northern industrial counterparts.  He feels that the real civil war is "the other" one not discussed because it pitted the wealthy few against the poor majority.