The Missouri Compromise: Both Maine and Missouri applied for statehood during a time when Congress was engaged in heated debate over slavery. There was a balance between the amount of slave and free states, and no congressman wanted to see the balance shift to the opposing side. Southern congressmen opposed admitting Maine into the Union as a free state, while northern congressmen opposed the admission of another slave state. Eventually, Congress compromised. Both Missouri and Maine were admitted into the Union: Missouri as a slave state and Maine as a free one.