Answer:
Maine and Missouri were admitted as a result of the Missouri Compromise of 1820.
Step-by-step explanation:
Missouri had applied for admittance, but they were a slave territory and their admittance would have caused an imbalance in the proportions of slave states to free states. Because of this Maine, which had previously been a part of Massachusetts, was admitted as a free state. This was done to keep the balance between the free and slave states.