Explain how the twin issues of expansion and slavery drove the sections apart in the 1830s and 1840s.

The U.S. acquired two large pieces of land in the 1830’s
and 1840’s where the issue of slavery was important and began to drive the northern
section of the country apart from the southern section of the country.  The land
acquired was Texas and the Mexican Cession. 

In 1836 Texas
gained its independence from Mexico and immediately asked the U.S. for annexation to the
U.S.  The debate over annexation centered on a couple of issues, one being slavery. 
Texas allowed slavery and the debate over whether to annex Texas pitted northern
interests that oppose slavery and annexation against southern interests who supported
slavery and annexation. This debate lasted 9 years until 1845 when Texas was admitted to
the Union as the twenty-eighth state, dividing north and
south.

The annexation of Texas sparked the Mexican American
War where an American victory led to the acquisition of the Mexican Cession, land that
included all of California, Nevada and Utah, and parts of Arizona, New Mexico, Colorado,
and Wyoming.  The issue of slavery in the new acquisition led to the Compromise of 1850
which deepened the division between north and south. In the compromise, California was
admitted as a free state and the slave trade was ended in the nation’s capital,
Washington, D.C.  These provisions upset the south.  Two new territories, New Mexico and
Utah, were established and slavery would be decided by popular sovereignty in these new
territories.  This meant that the people of the territory would decide the issue of
slavery, which opened up a huge area to slavery.  Also, a new fugitive slave law was
passed.  This mean that everyone, even people in the north, had to assist in returning
runaway slaves.  These provisions of the Compromise of 1850 upset people in the north. 
The Compromise of 1850 created tensions between the north and south, helping to drive
the two sections apart.