York State finished the Erie Canal, in 1825. The population increased so
rapidly, that six new states, west and south of the Allegheny Mountains,
were admitted between 1812 and 1821. A serious conflict arose in 1820
over the admission of Missouri. The Missouri Compromise resulted in the
prohibition of slavery in the Louisiana Purchase, north of 36° and 30'
north latitude. Missouri was admitted in 1831, and Maine, as a free
state, in 1820.

With the passing of protective tariff measures in 1816 a readjustment of
party lines took place. Protection brought over New England from
Federalism to Republicanism. Henry Clay of Kentucky was the leading
advocate of protection. Everybody was agreed upon this point in
believing that tariff was to benefit all classes. This time was known as
"The Era of Good Feeling."

Spain ceded Florida to the United States for $5,000,000.00, throwing in
claims in the Northwest, and the United States gave up her claim to
Texas. The treaty was signed in 1819.

The Monroe Doctrine was contained in the message that President Monroe
sent to Congress December 2, 1823. The colonies of South America had
revolted from Spain and had set up republics. The United States
recognised them in 1821. Spain called on Europe for assistance. In his
message to Congress, Monroe declared, "We could not view any
interposition for the purpose of oppressing them, or controlling in any
other manner their destiny by any European power, in any other light
than as a manifestation of an unfriendly feeling toward the United
States....The American Continents are henceforth not to be considered as
subjects for future colonisation by any European power." Great Britain
had previously suggested to Monroe that she would not support the