James Knox Polk was the right president at
the right time. He came to power amid  a growing sense of "Manifest
Destiny" that encouraged westward expansion and  imparted a sense
of duty to those moving toward the ever-growing frontiers.  Perhaps,
then, it is fitting that Polk grew up, for much of his life, on
the  frontier–then defined as Tennessee.
In 1795, when America was born, the country was still
struggling with how to  live under its new government. The Constitution had only
been adopted six years  prior, and Polk was only just beginning his
schooling when the War
of  1812 began. The whole political process–and  the
whole nation–was still being shaped.
Polk entered politics just as political parties began
to exercise great power.  Andrew Jackson's Democratic Party, based
largely on Jeffersonian principles of  democracy, had arisen and
now opposed the Whig Party, led by John Quincy Adams  and Henry
Clay. The Whigs favored higher tariffs and internal improvements.
 For his part, Jackson retired as the most popular president since
George  Washington and Polk so closely aligned himself with and
learned so much from  Jackson, whose nickname was "Old Hickory,"
that Polk earned the nickname "Young  Hickory."
Polk's expansionist ideas grew out of the same sense that
pervaded American  thinking in the late 1830s and 1840s. "Manifest Destiny"
held that the U.S. had  an almost divine right to expand across
the continent and bring its freedoms to  as many as possible. Texas,
an equally independent area, seceded from Mexico in  1835 and formed
its own country–much to the consternation of both the U.S.  and
Mexico. When Polk earned the Democratic nomination for the Presidency
it was  largely because he was one of the only politicians to forcefully
support the  annexation of Texas as a territory of the United States.
The issue of slavery, though, was the great divide during
Polk's career. The  Founders of the American Constitution had believed that
the issue would slowly  wither away and die of its own accord, that
there was no need to deal with it in  a long-term way. However, the
southern plantation owners believed that their  "peculiar institution"
was vital to the production and processing of cotton. As  the northern
states slowly became more industrial they outlawed slavery,  creating
a growing disconnect between slave and free states. Although the
issue  came up many times in Polk's political career, it would not
fully erupt until a  decade after his death–when the election of
Abraham Lincoln and the Civil
War split the nation in two.