In 1849 California requested permission to enter the Union as a free state, potentially upsetting the balance between the free and slave states in the U.S. Senate. Senator Henry Clay introduced a series of resolutions on January 29, 1850, in an attempt to seek a compromise and avert a crisis between North and South.
The southerners supported the compromise of 1850, because it gave them the opportunity to make more slave states.
The northerners were unhappy with the idea, because it meant that the new states could be slave states. It also started the Fugitive Slave Act.