Final answer:
Investigations into riots across U.S. history have found that they often began due to racial discrimination, economic struggle, and a lack of employment and safe housing, leading to violence against perceived symbols of oppression.
Step-by-step explanation:
The investigations into the various riots that took place throughout U.S. history, particularly in the late 19th and mid-20th centuries, revealed that a confluence of discontent due to racial injustices, economic hardship, and discrimination were at the heart of these uprisings. During the 1960s, for instance, African American communities experienced profound frustration over the lack of good healthcare, job opportunities, and safe housing, which created a fertile ground for riots, especially after events that acted as catalysts for expressing their anger. In the past, notably in the late 1800s and early 1900s, workers tired of enduring oppressive conditions from employers, landlords, and government, took to violence against the symbols of their oppression. Riots in urban neighborhoods often targeted stores that practiced discriminatory hiring or properties owned by slumlords known for abusing black tenants. Incidents like collisions between white and black men or arbitrary law enforcement practices could escalate into full-scale riots.