Slavery was firmly established in US at the verge of 18th century. Series of penal codes and statutes were enacted to regulate the activity. The Louisiana Purchase sparked political and geographical concerns of occupation from anti- and pro- slavery states. The Congress in 1820 wanted to split the newly attained territories into slave states as well as free states. An agreement known as the Missouri Compromise in the same year was signed between these two states to regulate the slavery in the western territories. This followed prohibition of slavery in the northern states bordering Arkansas but with an exemption of Missouri.
Missouri was admitted in a Union with Maine a year later and other states were restricted until 1836. Arkansas became a slave state and Michigan a year later became a free state. After 10 years when Mexican war broke, US Congress added a new territory. Gold rush in California led to increased population and demanded to be included as a free state. Washington D.C was the main slave Market within North America.
Henry Clay presented the Compromise of 1850 that saw California being endorsed to be a free state. Texas was told to pay $10 million to Mexico and relinquish the land they had disputed. Voters in New Mexico and Utah were left with the decision to be free or slave territories. Slavery was abolished in Columbia but retained in Washington D.C. The fugitive Slave Act was also passed in 1850 and granted the federal government the responsibility of apprehending fugitive slaves in the North. Many slaves who had started lives in North fled to Canada leading to population outburst there.
"Compromise of 1850." (2016) In American History Central, Retrieved April 27, 2016, from American History Central: http://www.americanhistorycentral.com/entry.php?rec=733
Robert E. May (2013). Slavery, Race, and Conquest in the Tropics: Lincoln, Douglas, and the Future of Latin America. Cambridge University Press, 7 Oct 2013 - History - 296 pages
Adam ROTHMAN (2009). Slave Country: American Expansion and the Origins of the Deep South. Harvard University Press, 30 Jun 2009 - History - 312 pages