The Compromise of 1850 was needed because of the territory gained from the Mexican War.

Answer 1

The Compromise of 1850 was necessary to be passed because it allowed California to enter the Union as a free state with a slave state accompanying it, however, with this being passed, there would be stricter fugitive slave laws implemented in the North which would allow Southern Plantation owners to regain their runaway slaves despite them being in "free territory." This led to many freedmen being wrongfully captured and brought back into slavery in the South.

It also brought forth popular sovereignty in dictating whether or not a new state could have slavery...basically making slavery legal almost everywhere.