U.S. Expansion – How the country became so large.

How did the United States grow from 13 separate British colonies along the Atlantic coast into one country that touches the Pacific Ocean?

The politics can be complicated but the general idea is relatively easy.  There were a few incidents that expanded U.S. lands in sizeable ways and two huge expansions.  We will cover the two large expansions.


The 13 colonies became states of a united country in 1776.  The current form of government was implemented in 1789.  Soon after that the country began to expand. The expansion of land was so large in the two major incidents to be discussed that the acquisition of Florida is considered small!  That may give you an idea of how much land the United States gained in these agreements.  (You probably know at least one of them.)  Some smaller land acquisitions:

Acquisition of Florida from Spain 1819.

Inclusion of Texas as a state 1845.

Gadsden Purchase from Mexico 1853.

Purchase of Alaska from Russia, 1867. (“Seward’s Folly”) – It should be noted that Alaska is absolutely huge, but it is not as politically important as what will be discussed below.


The two major incidents of expansion are the Louisiana Purchase and the land resulting from the Treaty of Guadalupe Hidalgo after the US – Mexican War.


The city of St. Louis and the area of Louisiana was named after Saint Louis, or Louis IX, king of France, who lived from 1214 to 1270.  He really was a “Saint” as he was canonized (made into a Saint by the Catholic Church) in 1297.  “Louis” is pronounced “Louey.”

In regards to the area of Louisiana, it was owned by France, obviously.  It was a massive area consisting of a large number of today’s states in the Midwest and West.  This land was acquired under Thomas Jefferson’s presidency.  At this time France was headed by the famous Napoleon, a leader not shy on expansion himself.

At this time, the western border of the U.S. was at the Mississippi River.  Due to its strategic and economic location on the Mississippi River, the United States attempted to get the city of New Orleans from France.  Instead, the United States was able to buy the whole Louisiana Territory.  Napoleon knew he needed to focus on Europe and that he couldn’t really control this territory.  What really showed him this was the slave rebellion in France-controlled Haiti, which is located in the Caribbean.  The French could not control the situation.  Haiti soon became independent, and the first free black nation in the Western Hemisphere.

The opportunity to buy the Louisiana Territory came as a surprise to many, especially Jefferson.  The president did not really find anything in the Constitution enabling him to purchase the territory but that did not stop him. The huge area was purchased in 1803.


The next large expansion didn’t occur until over 40 years later.  The country of Mexico, newly independent from Spain in 1810, Mexico claimed all the land in North America formerly claimed by Spain.  Soon, the U.S. would claim much of the same territory. The acquisition of the Mexican Territory was accomplished by way of war.

The war with Mexico remains controversial.  California was a very large jewel that the United States wanted. The United States was expanding in population and power.  The Mexican territory was sparsely populated in relation to the eastern portion of the continent.  There was also a border dispute with Texas – Mexico claimed the Nueces River to the north, the U.S. claimed the Rio Grande to the south.

War erupted in 1846 with the U.S. claiming violence was committed against U.S. troops by Mexican troops in the disputed area between the two rivers.  Future president Abraham Lincoln made his famous “Spot Resolution” in Congress, urging President Polk to show the “spot” on which American blood was spilled.  (This was an anti-war speech.)

The war was generally popular.  The idea of “Manifest Destiny,” the idea that the U.S. was destined by God to stretch from the Atlantic to the Pacific, was put into the national mind by newspaper editor John O’ Sullivan in 1945.  Mexico was standing in the way of Manifest Destiny.

The U.S. military soundly defeated the Mexican army.  Many Civil War generals from the North and South fought together as lower ranking officers in this conflict.  The Treaty of Guadalupe Hidalgo ended the war in 1848.


The map below shows in detail the areas of United States expansion with dates.  The map was taken from thomaslegion.net.







Author: historymadesimpleblog

I live in Salt Lake City, Utah with my beautiful wife Ashely. I have a BA in History. I am a USAF and US Navy veteran and I currently serve in the Utah National Guard. I am a realtor with Keller Williams South Valley (Riverton, UT) and I am an investor in real estate. If you like my blog or get anything out of it please do one or some of the following: - Go to a thrift store and buy some decent books to donate to your local school. - Please spread my name to anyone in Utah who needs to buy a house, sell a house, or wishes to invest in real estate. jaylalik@kw.com

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