Many riots erupted in Northern cities as a result of

A. The thousands of northern men who died in the war thus far

B. Lincoln using conscription as a way to increase the number of Union soldiers

C. Lincoln issuing the Emancipation Proclamation, because many Northerners felt African Americans would

migrate North become competition for getting jobs

D. Lincoln failing to find a good leader to assign the position of Union General

C.

Explanation:

Although the riot was originally against the draft, it quickly became racially charged against black people. As the rioters believed that the liberation of black slaves and their subsequent migration to the Union would saturate the labor market, and create greater competition for white middle-class immigrant workers.

It is also worthy to note that the dependancy of NYC on the cotton trade with the South was also another reason for the general discontent against the draft and the war itself.