Final answer:
The Missouri Compromise of 1820 aimed to maintain the balance between slave and free states by admitting Missouri as a slave state and Maine as a free state, and by introducing the Thomas Proviso that banned slavery north of the 36°30' line. This compromise was pivotal in addressing the expansion of slavery, but underscored the growing division within the country.
Step-by-step explanation:
The key provisions of the Missouri Compromise of 1820, led by Henry Clay, were primarily about addressing the balance between slave and free states. It included the admission of Missouri as a slave state and Maine as a free state, maintaining the balance in the Senate. Additionally, the Thomas Proviso was introduced, which prohibited slavery above the 36°30' line in the Louisiana Purchase territory, excluding Missouri. This legislative act was a pivotal attempt to quell the growing sectionalism and controversy over the expansion of slavery, which was fracturing the young nation.
These measures aimed at placating both Northern concerns over the spread of slavery and Southern fears about losing influence in the Senate. However, the Missouri Compromise also highlighted significant disputes within the country, such as whether the framers of the Constitution intended for the expansion of slavery, and rekindled arguments over the meaning of 'All Men Are Created Equal'. Whilst providing a temporary solution, the compromise exposed the deepening divide over slavery, a conflict that would continue to simmer until the Civil War.