The War of 1812 between the United State and Great Britain, which lasted from 1812 to 1815, was conducted mainly from Lake Champlain to Montreal, along the Canadian border at Niagara and Detroit, along the Gulf of Mexico, and at sea.

The grievances of the United States consisted of Britain's slow removal of itself after the conclusion of the Revolutionary War some 30 years before, the unfavorable or lack of trade agreements between the United States and Britain and the thwarting of U. S./France trade by British blockade, and incidents at sea involving the impressment of American citizens.

War was declared by the United States at a time when the Napoleonic Wars were concluding, freeing up men and funds for Great Britain to use against the United States.  The British invaded, and the war resulted in battles largely unfavorable to the United States and the burning of Washington, D. C.  The Battle of Plattsburgh Bay on Lake Champlain was the final battle in the north and was a defeat upon the British fleet by Thomas McDonough leading to the retreat by the British into Canada. The last battle of the war, the Battle of New Orleans, was fought after the treaty ending the war was signed   In this battle Andrew Jackson defeated the British attempt to take that city.

The cause of the war between the United States and its neighbor, Mexico, was due mainly to the expansionist desires of the United States.  At that time, Texas was an independent state, recognized by the United States and Mexico.  By procedures not used with other states when joining the Union, it was effectively annexed by the United States.  Mexico had similar designs. But it was expansion to the west, largely possessions of Mexico, including the vast area on the Pacific coast made up of present day California, Nevada, Utah, Arizona, and New Mexico, which was coveted by the administration of President Polk of the United States. Mexico lost the war and these possessions would become part of the United States.