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

Answer 1

Following the Mexican-American War, new western territories became available as potential new U.S. states. The issue of whether these new territories would be slave of free states was a massive debate in an evenly divided nation of slave and free states in the U.S. Senate. A new compromise was needed to replace the Missouri Compromise/Compromise of 1820. That compromise had previously allowed states to enter the Union in pairs, 1 slave and 1 free.

The pressing issue in 1850 was that California applied to join the Union as a free state, but abolitionists would not allow additional new slave states to join the Union. Because the previous compromise broke down the new compromise allowed California to enter as a free state in exchange for a stringent Fugitive Slave Act to capture runaway slaves in free states.