Lorain, Ohio in 1941; the Rural South in the Early 20th Century
The novel begins in Ohio after the Great Depression. Economic security is of particular concern for African Americans, who have far fewer opportunities for mobility than do their white counterparts. From the beginning, we see how important every last penny is to the MacTeers, as their entire family spends time picking coal for Zick's Coal Company even though it harms their health.
When we get to Pauline's and Cholly's stories, we can view their moves north to Ohio from the South as part of the Great Migration of African Americans that occurred from 1910 to 1940. Waves of African Americans seeking better jobs and more racial tolerance moved from rural southern towns to more industrial northern ones.
Of course, when Pauline and Cholly arrive in the North, their lives don't necessarily change for the better, and this geographical complexity is one of the most important aspects of the novel. Once up North, the couple has to face a different set of problems: disdainful whites, people judging them on the basis of their southern accents, differing beauty norms, etc.
Through Soaphead Church, Morrison also tackles Caribbean immigration to the United States, albeit briefly.