What feelings were produced by the annexation of western lands in early mid 1800's?

Before the United States acquired the Louisiana Territory, the
port of New Orleans and the mouth of the Mississippi River were closed to Americans.  Americans
who lived between the Appalachian Mountains and the Mississippi River had to ship their produce
and import what they bought from overseas, through northeastern ports such as New York City,
Philadelphia, and Baltimore.  Thus northern and eastern merchants did not want the U. S. to own
the Louisiana Territory because this would make it easier and cheaper for trade to go through New
Orleans than through northeastern ports.

Almost from the start of
government under the Constitution, there were businessmen and politicians in the North who wanted
to use government to aid the growth of business.  At the same time there were politicians and
planters and yeomen in the South who did not want to pay the taxes that government aid to
business would entail.

When Louisiana was purchased, Northern
interests feared that more states would be created out of it that would be controlled by planters
and Southern yeomen and their politicians.  This would mean more senators and representatives who
would oppose Northern interests in Congress.  The Northern interests thought they would thus have
too little power in the federal government.  They were very upset about the Louisiana
Purchase.

When the territory taken from Mexico was added to the
U.S.,  Northern business and political interests tried to pass a law in Congress that would keep
slaveowners out of the new states that would be created from the territory.  This made
Southerners very upset, because whether they owned slaves or not, they did not want to see
Northerners achieve unchallanged control of the federal government.