From the turn of the 19th century until World War II, the incidence of significant domestic unrest mostly involved labor disputes or what?

The correct response highlights that from the turn of the 19th century until World War II, significant domestic unrest primarily involved ideological discord alongside labor disputes. This period experienced a range of ideologies competing for influence within the American political landscape, including socialism, anarchism, and various nationalist movements. These ideologies often led to heightened tensions and unrest, manifesting in strikes, protests, and clashes between groups with fundamentally differing beliefs about government, economics, and individual rights.

During this timeframe, the labor movement was also significantly active, as workers organized to demand better wages, hours, and working conditions, which sometimes resulted in violent confrontations between labor forces and law enforcement or business owners. However, this labor struggle often intersected with broader ideological battles over social and economic structures. Therefore, recognizing ideological discord as a significant source of unrest helps to fully understand the volatile social climate of the time, as it encompassed not only workers' rights but also the competing visions of society and governance emerging from diverse ideological frameworks.