What was a significant effect of the Civil War?

The ending of Reconstruction is indeed a significant effect of the Civil War, as it marked the conclusion of a critical era in American history that sought to address the consequences of the Civil War, particularly regarding the integration of formerly enslaved individuals into society and the rebuilding of the South. After the Civil War, Reconstruction was initiated with various policies aimed at transforming Southern society, granting civil rights, and ensuring political representation for African Americans. However, by the late 1870s, the withdrawal of federal troops from the South led to the end of these efforts, resulting in the rise of Jim Crow laws and systemic disenfranchisement of African Americans.

The other options present notable historical contexts but do not reflect the immediate aftermath of the Civil War as significantly as the end of Reconstruction. The establishment of new trade agreements, while important, was not a direct result of the Civil War but more so an evolution in domestic and foreign policies following the war. The Confederacy, instead, was the entity that formed prior to the Civil War and its dissolution was a direct consequence of the war's outcome, not an effect. Improvements in military technology were indeed a feature of the war itself, influencing how battles were fought but not representing a significant societal or political outcome of the war