Question

The event that threatened to destroy the longstanding balance of free and slave states in the United States Senate was the

a. passage of the Kansas-Nebraska Act.
b. potential admission of Oregon as a free state.
c. attempt to acquire Cuba as a slave state. d. proposed building of a southern transcontinental railroad.
e. discovery of gold in California and its bid for statehood.

Answer 1

The Kansas-Nebraska Act, which allowed the possibility of slavery in new territories through popular sovereignty and led to violent conflicts and political shifts, threatened the balance of free and slave states in the U.S. Senate.

Step-by-step explanation:

Kansas-Nebraska Act:

The event that threatened the balance between free and slave states in the Senate was the passage of the Kansas-Nebraska Act.

The Kansas-Nebraska Act was highly significant because it effectively overturned the Missouri Compromise, which had previously regulated the extension of slavery in the United States. The Act, proposed by Stephen A. Douglas, divided the territory west of Missouri into two parts, Kansas and Nebraska, with the status of slavery to be decided by the concept of popular sovereignty—meaning the residents of each territory would determine whether they would allow slavery. This potentially opened these territories to slavery. It resulted in a period of violent conflict known as 'Bleeding Kansas' as pro-slavery and anti-slavery forces clashed over control of the territories. The Kansas-Nebraska Act also led to political upheaval, contributing to the collapse of the Second Party System, the rise of the Republican Party, and intensifying sectional tensions that ultimately edged the country closer to the Civil War.