Who benefited from the missouri compromise

Slaves supposedly in the North ...

It was, as the title states, a compromise; neither side gained a clear or decisive advantage. The legislation is credited with maintaining a truce between the North and South for another 30 years, postponing the splintering of the Union that came with the Civil War. It maintained the delicate balance between slave and free states in Congress by admitting Missouri as a slave state and Maryland as a free state. If there was any imbalance to the compromise, it might be in the fact that it prohibited the establishment of slavery in the remaining Louisiana Purchase territory that was North of the 36•30' parallel - - because that encompassed the largest portion of the remaining unsettled land in the Purchase.

(All of this compromising was repealed via the Kansas-Nebraska Act in 1854 and by the Dred Scott case that declared the Missouri Compromise to be unconstitutional, saying Congress did not have the authority to ban slavery in the territories.)