Final answer:
The Emancipation Proclamation was one of the most important events since the Revolutionary War as it marked a crucial step towards the abolition of slavery in the United States and indicated a shift in the focus of the Civil War.
Step-by-step explanation:
One of the most important events since the Revolutionary War is b) The Emancipation Proclamation. The signing of the Declaration of Independence was indeed a critical moment, but it preceded the Revolutionary War itself, which from 1775 to 1783, led to the founding of the United States. On the other hand, the Emancipation Proclamation, issued by President Abraham Lincoln on January 1, 1863, during the Civil War, declared that all slaves in Confederate-held territory were to be set free. This pivotal act marked a significant step towards the abolishment of slavery and underscored the Civil War's shift in focus toward a fight for human rights, ultimately leading to the 13th Amendment, which formally abolished slavery in the United States.
In broadening the context, events like the Civil Rights Movement and the Louisiana Purchase also played significant roles in shaping American history. The Civil Rights Movement of the 1950s and 1960s was crucial in the fight against segregation and discrimination, leading to landmark legislation like the Civil Rights Act of 1964. The Louisiana Purchase, completed in 1803, doubled the size of the United States and was instrumental in westward expansion.