Northern law makers convinced to Allow Missouri into the Union as a slave state under the Missouri compromise, because Maine was added to the United States as a free State.
Northern lawmakers were convinced to allow "Missouri" to be added as a "slave state" into the union under the "Missouri Compromise" because Maine was allowed to be added as a free state to the union.
EXPLANATION:
As slave state, Missouri was in many ways controlled by the Congress.
In fact, the Congress had the rights to make "laws regarding slavery" or its absence thereof from Missouri.
On the other hand, Maine had to the liberty not to choose slavery.
