In the history of the world, land expansion was rarely the result
of one country buying property from another.  No, it was through
wars and expropriation.  From Biblical times to the present,
borders changed about as often as one rogue group saw the need
for more than they had.  Until the group of people from Europe
ventured the uncharted seas to establish a colony in this new
world, built homes and settled down, land grants from one despot
to another was the rarity to expansion by conquest.  Then the
trading began and almost without exception, this country expanded
through purchases: Louisiana Purchase; Gadsden Purchase; Seward’s
Folly – the purchase of Alaska from Russia, etc.  And, yes, the
purchase of Manhattan from the Indian tribe in control.  As the
colonies grew and expanded, the trek west began and the history
of expansion into formerly “Indian lands” became an extremely
contested endeavor.  Indians had no “deeds” to land they occupied
and purchases were rare – deals were made.

In the Journals of Lewis and Clark, continual mention of the
migration of tribes following the animal herds was the life of
most tribes – land was not something to “own,” but only to serve
mankind until they were forced to move along with their food
source.  There were various peaceful tribes that were more prone
to farm than hunt – but they were few.  Let’s face it, farming is
tough business; shooting an elk, deer or bison was usually quick
and easy: spot game this morning; eat tonight.  And so, borders
were only recognized by one’s ability to keep others out until
they, themselves, were forced to move on.

I was born and raised in Sakakawea’s village.  Actually, she and
her tribe had long since departed – they couldn’t wait for my
arrival.  Friends and I often hunted where her village once stood
and we would quite often feel that there was still a “presence”
of the spirit of the indomitable tribe that continually
maintained life in the Siberia of North America.  The land was
virtual prairie and was dotted with the remains of their
dwellings – cup-like indentations, now reverted to prairies once
again.  Some years ago the National Park Service acquired the
land from a private farmer and built the Knife River Indian
Village on the site to preserve a national treasure.  It’s well
worth a visit – and take your Lewis and Clark’s Journals along
when you visit.  Together, they give an account of the strength
and tenacity required of anyone attempting to live in a land so
forsaken of weather of any redeeming value.

When immigration was encouraged in the nineteenth century,
citizens of various European countries found new life in the
United States and land “free for homesteading” was touted in
newspapers throughout the land.  Many from other northern
European countries used to similar weather, took the challenge
and began moving west into central territories, often met with
Indian tribes still occupying such lands.  The history of these
relationships is still debated and they quite often led to
conflict.  In the end, some purchases were made, but more often
than not, the land was “traded” and present occupants were forced
to move on or were confined to reservations.  Such is the nature
of mankind: when in need of more than you have, expand:  buy,
conquer or trade – until there is no more.
http://www.nps.gov/knri/index.htm for more info.