What caused labor unrest in the United States after World War I?

The main causes of labor unrest after World War I included poor working conditions, income inequality among workers and low wages for the workers. After the war in 1919, there were more than 3,000 strikes, which caused more than four million people to quit their jobs.

After the war, many native American workers feared that their status was eroding. Unskilled and semi-skilled workers were substituted with craft workers, thus losing their jobs. Immigrants from Europe saturated the labor market, which resulted in lower incomes. This caused Americans to agitate for restriction of immigration. Some of the popular American strikes included the coal miners strike, Boston police strike and the steel mill strike.