National unity was at its peak during this short time, which would last for only a few years. Next, the Treaty of 1818 provided a joint occupation of Oregon with Britain, and also secured a treaty boundary that gave more territory to America than the natural boundary of the Missouri River would have given to America. Joint occupation reflected American nationalism in foreign policy; this nationalism signified strong national unity. The Treaty of 1818 created a boundary at the forty-ninth parallel, which provided the United States with more land than the Missouri River's natural boundary would have provided. Therefore, the sectionalist Federalists would not have agreed to this treaty because they were emphatically against expansion. Their opinion was ignored because it was minute. This further consolidated national unity because it showed that the people of America were generally in agreement with governmental decisions. Furthermore, as a result of the secured territory claim by the Treaty of 1818 in the American Northwest, the Monroe Doctrine was issued. The 1823 Monroe Doctrine was directed towards Europe, primarily at Russia who was threatening to invade the Northwest. This bold statement, issued to "protect" the new territory near Oregon, met no opposition in America and was made in part because of nationalism. Nationalistic gestures such as the Monroe Doctrine that meet little home opposition signify national unity. Between 1800 and 1823, national unity was boosted by expansion.
2.
Between 1819 and 1850 the Louisiana Purchase, annexation of Texas, Mexican .
Cession, and the addition of California led to national disunity. Sectional tensions, mainly because of slavery, were the main causes of national disunity. Although the Louisiana .
Purchase had a positive effect on unity as mentioned before, it had a negative effect .
on unity around 1819. The states being carved out of the Louisiana Purchase were being admitted alternately, free or slave.