It marked the turning point because it’s a union battle and it would be a win for the north not the south.
Hope this helps.
The Missouri Compromise was the laws that enacted in 1820 to maintain the balance of power between slave and free states. Henry Clay wanted Missouri (state) to be a free or a slave state but the Southerns claimed that the Constitution did not give the Congress the power to ban slavery. THey would worry that if free states formed a majority in Congress, they would ban slavery altogether. Meanwhile, Maine wanted to be part of the statehood, so Henry Clay suggested that Missouri could be a slave state and Maine as a free state but the Congress passes the Missouri Compromise so Maine became a free state and Missouri as a slave state (I think?). Among these tensions, the Mason Dixon line formed the Maryland and PA border. The line came to be used for the division between the slave states and free states, as well as the division between the north and south.(I hoped I answered your question!!)
