Final answer:
The antiracist effects of the Civil War were most notable in the North and Upper South with the legislative abolition of slavery and the beginnings of African American empowerment, but pervasive racism and Black codes still presented major challenges.
Step-by-step explanation:
The antiracist effects of the Civil War were most notable in the legislative changes and societal shifts that occurred, primarily in the North and to some degree in the Upper South. After the war, the Thirteenth Amendment abolished slavery, and African Americans began to obtain rights and hold public offices—events that significantly altered the social and political landscape. Despite these progressive changes, racism persisted nationwide, and African Americans faced systemic challenges, including Black codes in the South, housing shortages, and discrimination across the country. The fight against these injustices laid the groundwork for the civil rights movements that emerged in the 20th century.