The Treaty of 1818 with Britain fixed the northern United States border at the 49th parallel, confirming the Red River Basin as American, while providing for joint settlement of the Oregon Country. In the south, Andrew Jacksons 1817–18 Seminole War led, through its overenthusiastic prosecution, to the occupation of much of northern Florida. The colonial power, Spain, bowed to the ‘facts on the ground’ and ceded Florida in 1819. Despite war with Britain (1812–14), the flow of new states continued. Louisiana (1812) was followed by Illinois and Indiana in 1816. Detroit, captured from the British, became effective capital of the newly organized Michigan Territory in 1818. Arkansas territory was carved out of the vast Missouri Territory (1819), after Alabama and Mississippis admission to the Union. The District of Maine was admitted as a state in 1820, conditional upon the hotly disputed Missouri Compromise, the harbinger of future North/South conflict.
— OR —