Final answer:
In the 1870s, Republicans in Congress began focusing on the economic growth of the United States, moving away from active involvement in Southern Reconstruction, due to societal pressures and political changes following the Panic of 1873.
Step-by-step explanation:
During the 1870s, Republicans in Congress shifted their attention from Reconstruction to focusing on the economic growth of the United States. This shift was influenced by a few factors, including the ongoing problems in the South, the Panic of 1873, and the midterm election results of 1874, which demonstrated a clear desire among voters for the government to prioritize economic recovery. The Republican majority in the House was significantly reduced, and Democrats made gains in the Senate, indicating that support for additional enforcement measures for the Reconstruction was waning. Instead, the government passed the Civil Rights Act of 1875 and subsequently devoted less effort to prop up the southern governments, signaling a de facto end to substantial federal involvement in Reconstruction policies.