Answer:
The domestic shift that most affected the demographic makeup of northern US cities in the early 1900s was the migration of African Americans from southern farms to northern factories during the Great Migration.
Step-by-step explanation:
It is called Great Migration to the displacement of 1.75 million African Americans from the southern states to the midwest, northwest and west of the United States. It took place from 1915 to 1930.
When the Emancipation Proclamation was signed in 1863 less than eight percent of African-Americans lived in the northeastern or midwestern states of the United States. As late as 1900 ninety percent of blacks lived in formerly slave states.
Between 1910 and 1930 the black population of the United States grew 40% in the northern states, concentrating this increase in the big cities such as Chicago, Detroit, New York, and Cleveland.