The territorial expansion can be seen as splitting the nation apart when Missouri was added to the nation from 1819-1821. In 1817 Missouri applied to the Union as a slave state. The House of Representatives passed the Tallmadge amendment, twice, which stated that no more slaves should be brought into Missouri. The south was angered by the new amendment and saw it
as a threat to sectional balance of north and south United States. The Tallmadge amendment was later turned down by the Senate. In December of 1819, Maine applied to become a free state. A compromise was reached where Maine would enter the Union as a free state, and Missouri would enter the Union as a slave state to keep the balance of north and south. The territory of the Louisiana Purchase north of the line 36o30' prohibited slavery. This is now known as the Missouri Compromise. Although it seemed like the north and south was united in a way that they kept the balance of the number of slave states versus the number of Free states, the beginning of sectionalism was beginning to take place.
Although, from 1800 - 1850 America saw a growth in territorial expansion the territorial expansion did not aid the nation into becoming unified, but rather tore the nation apart. The slavery issue of the northern and southern states shows the splitting of the nation and ten years later America plunged into the Civil War.