Context: During the late 1850s, Americans were divided over the issue of slavery. On occasion, the Supreme Court ruled on important cases that involved slavery. These court decisions shaped many Americans' opinions about slavery.
In 1857, the Supreme Court made an important decision about slavery in the case Dred Scott v. Sandford. Dred Scott was an enslaved person who argued that he should be free. The following map shows two places where Dred Scott's master took him to live in the 1830s. Look at the map. Then answer the question below.
Based on the map, why did Dred Scott believe he should be free after living at these two places?
A. Fort Armstrong was in a free state and Fort Snelling was in a free territory.
B. Fort Armstrong was in a slave territory and Fort Snelling was in a free state.
C. Fort Snelling and Fort Armstrong were both in free states.
D. Fort Snelling and Fort Armstrong were both in slave states.
Select the correct answer from the given choices and respond with the letter of the chosen option.

A