Whether intentional or not, Eli Whitney's cotton gin resulted in an increase of slave numbers throughout the American South, as the southern economy became more heavily dependent upon upland short cotton.

In the era of America’s Founding Fathers, most prominent thinkers thought that it might take as much as a thousand years to settle the entirety of the continent under one national entity. Due largely to the invention and widespread construction of Railroads this was achieved in a mere few decades. Railroads helped promote trade across the continent and further afield – enabling goods from the Far East to be shipped back to the Eastern seaboard. It encouraged the growth of urban communities which could be much more easily sustained by railroad trade. And, not insignificantly, it provided for the first time a far easier means for tourists from the East to travel to places like Yosemite to witness the wonders of America’s, as of yet not established, National Parks—which in turn lead to much wider support for legislation to protect them. It did not, however, improve American relations with Native American communities—one might suspect that the removal of the massive boundary of space might have resulted in the reduction of the perception of Native Americans as an “other” group to be feared; on the contrary, it allowed Americans to move en masse to territories occupied by Native Americans, and made it much easier to keep supply lines reinforced. 

The Pony Express was known for it's speed and reliability, but the new telegraph lines, once complete, were much cheaper and more efficient. This development rendered the Pony Express obsolete in a mere 18 months.

Irish immigrants had come to America since the first Europeans arrived, but the first large migration occurred in the 1840s and 1850s. The biggest reason for this was the Irish Potato Famine that began in 1845. The famine was exacerbated when the British government refused to give any assistance. Estimates are that as many as 1 million Irish died during the famine, while another million emigrated elsewhere, chiefly to the Northern cities of the United States.

In the aftermath of the XYZ Affair and straining relations with France, the Federalists passed the Alien and Sedition Acts, which outlawed anti-government activity, lengthened the residency time required for naturalization of foreigners, and allowed the President to imprison or deport aliens who he deemed dangerous to American peace and safety. The laws were unpopular with many Americans due to their authoritative nature, leading to increased support for Thomas Jefferson and the Democratic-Republicans at the expense of John Adams and the Federalists.