Final answer:
The Missouri Compromise of 1820 allowed Maine to enter the Union as a free state and Missouri as a slave state, as well as establishing the 36°30' line to limit the expansion of slavery in territories.
Step-by-step explanation:
The Missouri Compromise of 1820 led to several significant outcomes in the political landscape of the United States regarding the issue of slavery. Through the efforts of Henry Clay and others, the Compromise resulted in Maine entering the Union as a free state and Missouri entering as a slave state. Additionally, it established the 36°30' line, north of which slavery was banned in the remaining territories within the Louisiana Purchase, with the exception of Missouri. This compromise attempted to preserve the balance of power between slave and free states and subsequently dampen the growing tensions over the issue of slavery.