Final answer:
The Missouri Compromise included the admission of Maine as a free state, Missouri as a slave state, and the establishment of the 36°30' line to limit slavery's expansion in the Louisiana Purchase.
Step-by-step explanation:
One of the requirements of the Missouri Compromise of 1820, which allowed Missouri to enter the Union as a slave state, was that Maine would be admitted to the Union as a free state. This compromise, engineered by Henry Clay, was designed to maintain the balance of power between slave and free states in the Senate. To address the concerns about the expansion of slavery, the compromise also established a dividing line at the parallel 36°30' north latitude, north of which slavery was banned in the remaining territory of the Louisiana Purchase, excluding Missouri.