The period mentioned in the question starts around 1850. The correct alternatives are:
1) Civil War: War between the Union and the Confederate States came to an end in 1865. The Union emerged victoriously and started the process of annexation of the Confederate States to the political system of the country.
2) Millions of freed slaves: President Lincoln abolished slavery in 1863. This resulted in approximately 3.5 million slaves being freed.
6) Women's Suffrage Movements: These movements originated a couple of years before 1850 and lasted around 50 years.
7) Native American Wars: Ongoing wars that occurred as a result of the expansion of the US across the continent.
8) Burgeoning City Populations: Populations of the new settlements due to expansionism started to grow due to the emergence of businesses such as the Cotton Industry.