Complex sentence: During World War II both the economic activity and the physical decay of Black Bottom rapidly increased, and in the 1960s, the City of Detroit conducted an urban renewal program to combat what it called "urban blight" that bulldozed Black Bottom.
Split into simpler sentences: During World War II, both the economic activity and the physical decay of Black Bottom rapidly increased. In the 1960s, the City of Detroit conducted an urban renewal program to combat what it called "urban blight" that bulldozed Black Bottom.