Answer:
The period of westward expansion led Americans to expand the United States from the Atlantic Ocean to the Pacific Ocean.
Explanation:
From the 18th to the 19th century, the newly independent United States still formed a small country that stretched vertically between Maine and Florida and horizontally between the Atlantic coast and the Mississippi.
In the first census, in 1790, the country already had 2.3 million square kilometers and 3.9 million inhabitants. Starting withan aggressive policy of territorial expansion to the west, Americans created one of the largest nations in the world with an area of 9.8 million square kilometers in about a century.
Even before independence, American settlers already coveted the western lands, which were prevented from being colonized by the Quebec Act (part of the Intolerable Acts of 1774), which prohibited settlers from occupying land between the Appalachian Mountains and the Mississippi. Despite such pressures, westward expansion gained momentum after independence, being ideologically fueled by the "Manifest Destiny."
To attract people's interest, the federal government began to offer land at very low prices. Parallel to the expansion of its borders, the United States received successive waves of immigrants (almost 5 million people from 1850 to 1870). Thus, a wave of immigrants ventured to explore the interior of the American continent. To further expand its territorial expansion, the United States seized large territorial portions, either through diplomatic agreements or through war.
This occupational process was boosted by the construction of railways, which allowed the flow of productions from the west to the east, in the phase of urbanization and industrialization. The US also sought, with these railways, to march westward and secure possession of the conquered territories, encouraging immigration. In 1860, the country already had about 50 thousand kilometers of railroad. In 1869, America's first transcontinental railroad, connecting the Atlantic to the Pacific, was completed.
