Final answer:
The Missouri Compromise admitted Missouri as a slave state and Maine as a free state, banning slavery north of the 36°30' latitude line. Option D is the correct answer.
Step-by-step explanation:
The Missouri Compromise, crafted by Henry Clay and enacted in 1820, was a significant event in the history of the United States which attempted to balance the number of slave and free states in the Union. This compromise led to Maine being admitted as a free state and Missouri as a slave state, acknowledging Maine's petition for statehood which had followed Missouri's.
To address the sectional disputes and to manage the future expansion of slavery, a boundary was set at latitude 36°30'—north of this line slavery was banned, with the exception of Missouri, for all Louisiana Purchase lands. Therefore, the correct statement about the Missouri Compromise is D. Banned slavery above the 36-30 north line of latitude in the United States.