Since the Seven Years’ war (1754-1763), American colonies experienced gradual expansion. The territory of modern Quebec annexed after the war became after the end of the revolutionary wars the refuge of all British loyalists. After the revolution, 13 states formed a federation to ensure self-defense and successful development. In 1787, the United States Constitution was adopted and in 1788 it was ratified. American revolution opened to Americans the possibility to colonize the territory beyond the Appalachian mountains. It was the beginning of continuous drive to the west. In 1804, the territory of Louisiana was purchased from France. In 1819, Florida became a part of the US in accordance with the Adams-Onis Treaty. An expedition of Lewis and Clark sent by president Jefferson in 1804-1806 travelled across the continent and reached the Pacific Ocean exploring the lands. In 1848, as a result of the American-Mexican war, The USA acquired the modern-day territories of California, Nevada, Utah, Arizona and New Mexico. As a result of the above expansions, the number of American states increased from initial 13 to 34 by 1860. American colonization of western territories resulted in massive expulsion and extermination of native tribes which fiercely resisted to white colonists. War of 1812, Seminole Wars (1816-1858), Creek War, Texas–Indian wars (1820 – 1875), Cayuse War (1847–1855). In 1830, by the Indian Removal Act, all Indian tribes (Choctaws, Chickasaws, Cherokees, Seminoles, and Creeks) had to move from their native lands to the Indian Territory (Oklahoma). During this forced travel 4000 Indians out 15 000 died of exhaustion and starvation. Americans did a lot to develop the infrastructure of their country. The Erie Canal built in 1840 connected the Erie Lake with New York transforming this city into the most important port of the eastern coast.
600 kms. In totality, 3000 miles of canals were built between 1817 and 1840. The first railroad was built in 1828. The mileage of American railroad grew from 5, 000 in 1848 to 30 000 miles by 1860. The California Gold rush of 1848-1855 considerably contributed to the development of the west coast. The population of the country grew from 3.9 m in 1790 to 31 million in 1860.
The population of the southern states was 9 million and 20 m in the north. The north of the country was industrially developed and supplied necessary industrial goods to the rest of the country.