The problem with taking so much territory from Mexico in the Mexican-American War was that no system existed to determine whether or not the new states would be slave or free.
The Compromise of 1850 reassured both the North and South in that it admitted one free state and one slave state, and the balance in Congress between pro and anti-slavery Senators and Representatives was maintained. Secondly, both sides agreed that from that point on, popular sovereignty would decide the status of each new state. That means each state would vote yes or no on slavery and the majority would win.
Lastly, the South wanted to be reassured that rnuaway slaves were not being helped by abolitionists in the North, so the Fugitive Slave Act was included in the compromise, which made it illegal to aid runaway slaves in the North.
The Founding Fathers drew heavily upon English philosopher John Locke in establishing America's First Principles, mostly the recognition of unalienable rights, the Social Compact, and limited government.
