Final answer:
Before the Civil War, the prosperous states were in the South due to the wealth generated from slave labor in agriculture. After the war, prosperity shifted to the industrialized North, as reconstruction policies favored growth there. African labor continued to be exploited in the South, slowing its economic recovery.
Step-by-step explanation:
Before the U.S. Civil War, the most prosperous states were predominantly in the South due to their robust agricultural economy, which was heavily reliant on the labor of African American slaves in the cotton and tobacco plantations. Slave labor in the antebellum South generated great wealth for plantation owners, making the region economically dominant. The profitability of cotton, also known as 'King Cotton,' was especially crucial as it fueled profits for both Southern planters and Northern cotton mill industries.
After the war, the economic center of gravity shifted towards the industrialized North due to massive industrialization and economic growth. The policies enacted during the Civil War, such as the Homestead Act and the Pacific Railway Acts, contributed to this growth by promoting western migration and the expansion of railroads. While the South struggled with the destruction of its infrastructure and the challenges of Reconstruction, Northern cities and industries flourished.
The role of African labor shifted after the war. Many of the newly freed slaves remained as poor agricultural workers in the South, facing economic hardship and limited opportunities due to prevailing racist attitudes and a lack of capital in the devastated Southern economy. Thus, despite emancipation, their labor continued to be exploited, reinforcing the South's slow recovery compared to the more diversified economy of the North.