After the War of 1812, the first expansionist goal of the republic was the acquisition of Canada.
The War of 1812, war between United States and Great Britain, and Britain's Indian allies that lasted from 1812 to 1815.
Jefferson predicted in late 1812, "the acquisition of Canada this year, as far as the neighborhood of Quebec, will be a mere matter of marching, and will give us the experience for the attack on Halifax, the next and final expulsion of England from the American continent.