What are the main aspects of the territorial expansion of the United States in modern times?

1. Peaceful expansion

After taking office as President of the United States in 1803, Thomas Jefferson focused on the Mississippi River Basin and was eager to acquire the Pacific Coast, East and West Florida, Cuba and the Central American Canal. On January 11, Jefferson sent Monroe as a special envoy to France to negotiate. At this time, a black uprising broke out in France's Haitian colony. Napoleon sent troops to suppress it, but suffered a disastrous defeat. After losing Haiti, Napoleon was no longer interested in maintaining the colony of Louisiana, which he had recovered from Spain through the Treaty of San Aldefonso on October 1, 1800. The United States took full advantage of this situation, especially the conflicts between Britain and France after the Treaty of Amiens, and proposed the Louisiana Purchase to France. France agrees with this. After bargaining, the two parties reached an agreement at a total price of 80 million francs. On April 30, 1803, France signed the Treaty of Transfer of Louisiana with the United States. The United States actually purchased the entire 828,000 square miles of Louisiana for $15 million, or 3 cents per acre. As a result, the United States laid the foundation for its status as a great power. In this regard, Napoleon said this: "Entering this territory will ensure that the position of the United States will always stand firm, and I will create for Britain a maritime opponent that will sooner or later defeat its edge."

2. Taking advantage of the situation to advance

With this, the United States will also expand its territory to Florida and Texas. In fact, as early as 1795, the United States signed the "Pinckney Treaty" with Spain, also known as the "Treaty of Lorenzo", and obtained the right of free navigation on the Lower Mississippi River and the three-year "right of storage" in New Orleans. Created conditions for the United States to invade Spanish territory in the Americas. After the Treaty of Transfer of Louisiana was signed, the United States took advantage of the fact that the treaty did not clearly stipulate the boundary line of Louisiana. It passed the "Morby Act" on February 24, 1804, establishing an administrative region in the Mississippi River Basin, called "Mississippi Territory Separate Tariff". District,” bringing Florida into administrative jurisdiction. The United States used this as a basis to propose territorial claims to West Florida to Spain. This request of the United States was rejected by Spain. However, in 1810, the United States took advantage of the revolution in the Spanish American colonies and planned a series of rebellions by American farmers in East and West Florida. In early 1811, the United States sent troops to occupy West Florida. The American-British War broke out from 1812 to 1814. During the war, the United States defeated Spain and occupied 2/3 of Alabama, East and West Florida and its adjacent areas, and annexed West Florida to the Mississippi region of the United States. In addition, the United States also destroyed the Indian tribal alliances and gradually occupied the Indian land in the Lake Michigan area. By 1819, the United States took advantage of the raging uprising in Spanish American colonies and legalized the occupation and annexation of more than 100,000 square kilometers of land in east and west Florida by paying Spain $5 million, bringing the territory to more than 4.6 million square kilometers. kilometers, equivalent to more than half of the current territory.

3. Expansion to the north and west

In 1818, the United States and Britain held northwest boundary negotiations, located in Oregon between the Rocky Mountains and the Pacific Ocean, from 42 degrees to 54 degrees 40 minutes north latitude. A compromise agreement was reached on the ownership of the disputed area between the United States (including parts of the present-day states of Washington, Oregon, Idaho, Montana, and Wyoming in the United States and half of British Columbia in Canada).

: From Lake of the Woods to the top of the Rocky Mountains, bounded by the 49th parallel north, Oregon, located to the west of the Rocky Mountains, was administered by the British and American governments within 10 years and was free and open to citizens and subjects of both countries. In 1827, the United States and Britain reached an agreement to extend the administrative control of the Oregon Territory. However, disputes between the two parties have continued since then. By the early 1840s, the United States requested that all of this land under the jurisdiction of the United States be transferred to the United States, but the United Kingdom refused. For a time, the United States and Britain were at war with each other. In 1846, the relationship between the United States and Mexico was tense due to the Texas issue, and the U.S.-Mexican War was imminent. In order to avoid being attacked from both sides, the United States decided to compromise with Britain.

On June 15, 1846, the United States and Britain signed the "Oregon Treaty". Both parties agreed to end the administrative control of the Oregon region and divide Oregon into two parts at the 49th parallel north. This line extended westward to Puget. Bay, from where it enters the sea through the Strait of Juan de Fuca, leaving Vancouver Island on the Canadian side of the border. After that, the two sides had disputes over the exact location and direction of the boundary line in the Strait of Juan de Fuca and the ownership of San Juan Island. In the 1870s, the dispute was submitted to arbitration and was finally resolved. Transferred San Juan Island to the United States. Through the above-mentioned agreement, the United States acquired more than 700,000 square kilometers of land and expanded its territory to the Pacific Coast. In addition to the above, on December 29, 1837, British troops entered the United States and burned the American transport ship "Caroline" supporting the Canadian rebels, causing the "Caroline" incident and causing tension on the U.S.-Canada border. 1839 In February, residents of Maine in the United States and New Brunswick in Canada continued to complain about disputes over about 12,000 square miles of land on the Maine-New Brunswick border that was not settled by the 1783 Treaty of Paris. The area of ????the Aroostook River Basin immigrated, occupied and competed for land, resulting in border conflicts. The two sides negotiated a temporary settlement, with the Maine militia continuing to control the lands it occupied in the Aroostook River Basin, and New Brunswick retaining control of the settlements it had established in the Upper St. John River Basin and the unfinished provinces in the upper reaches. Blocked traffic lines. On August 9, 1842, the United States and Britain signed the Webster-Ashburton Treaty in Washington, which assigned 5,000 square miles of the disputed land near the north to Canada and 7,000 square miles near the south to the United States; the United States and Britain Citizens and subjects of both countries could freely navigate the St. Johns River; the 45th parallel was the northern boundary of New York and Vermont; the United States obtained approximately 200 square miles of land near the source of the Connecticut River. In addition, the treaty delineated a boundary line from Lake Superior to Lake of the Woods, and the United States gained approximately 6,500 square miles of disputed land. At this point, the U.S.-Canada border east of Lake of the Woods was fully delineated.

4. Expansion to the West and South

Before 1821, the vast area in what is now the southwestern United States, from Texas on the Gulf Coast to California on the Pacific Coast, was a Spanish colony. In 1821, Mexico gained independence from Spanish colonial rule, and the above areas became Mexican territory. After that, Americans began to immigrate to Texas. In 1835, immigrants from the United States to the Texas Province of Mexico launched an armed rebellion. In March of the following year, they expelled the Mexican army and established the Republic of Texas, also known as the "Lone Star State." On May 14, 1836, the Mexican army failed to suppress the Texas rebellion and was forced to sign a treaty recognizing Texas independence. After Texas became independent, it requested to be incorporated into the United States and become a state of the United States. However, at that time, the conflict between the North and the South was acute. The North was worried that Texas becoming a state would strengthen the power of the South in Congress, and therefore opposed the annexation of Texas. By 1844, the North and the South had compromised and decided to annex Texas. In April 1844, the United States and Texas signed a treaty of annexation. On March 1, 1845, the United States ratified the Treaty of Incorporation, and on June 23, a special session of the Texas Congress approved the Treaty of Incorporation. On December 29 of the same year, the United States officially annexed Texas to the United States, making it the 28th state of the United States. Mexico was furious at the U.S. annexation of Texas and severed ties with the United States. In 1846, US President Polk sent troops into the disputed area on the border between the two countries. Mexico lodged a strong protest. On April 24, a small conflict broke out between the Mexican army and the US military, killing three Americans. This incident just gave the United States an excuse. On May 13, the United States declared war on Mexico, and the U.S.-Mexico War broke out. The United States sent 50,000 troops to invade Mexico by land and sea. In July and August, the United States successively occupied some important towns in Mexico and declared New Mexico and California as US territories. On September 14, the United States captured Mexico City.

On February 2, 1848, the United States and Mexico signed the Treaty of Guadalupe Hidalgo: Mexico formally ceded Texas, New Mexico, and California to the United States, and recognized the Rio Grande River as the border between the United States and Mexico. The land acquired by the United States includes the six states of present-day Texas, New Mexico, Arizona, Utah, Nevada, California, and parts of Wyoming and Colorado. On December 30, 1853, the United States forcibly purchased approximately 45,535 square miles of the Gila River Basin south of the Gila River in southern Arizona from Mexico for $10 million, citing the need to build a railroad to California. The United States used military conquest, political diplomacy, and forced purchases to seize approximately 55% of Mexico's original land area, approximately more than 2.3 million square kilometers. At this point, the United States has basically completed its territorial expansion and occupation of its adjacent areas. By the mid-19th century, the United States stretched from the Atlantic to the Pacific, accounting for approximately half of the North American continent. The United States continued to immigrate to these new territories, and new states were established one by one and joined the Union one after another. In 1912, the United States established 48 states in the mainland.

5. Overseas expansion

As early as 1820 to 1822, the United States established its earliest colonial stronghold, Liberia, in West Africa. From 1861 to 1865, the Civil War broke out in the United States. The North led by President Lincoln defeated the South, abolished slavery, and maintained national unity. After the Civil War, the United States accelerated its overseas expansion. At the beginning of the 19th century, the Tlingit Indian tribe, which had lived in southern Alaska for generations, fought two wars with the invading Russians, and was finally conquered by the powerful Russians. However, after the Crimean War in 1856, Russia's vitality was severely weakened, and Tsar Alexander II decided to sell this land. In March 1867, Russia sent personnel to the United States to discuss the sale of Alaska. On March 30, 1867, the United States and Russia signed the Treaty of Transfer of Alaska. The United States purchased Alaska, located in the northwest corner of North America, and the surrounding Aleutian Islands from Russia for US$7.2 million, with a total area of ??more than 1.5 million square kilometers. . It is estimated that there are 5.7 trillion cubic meters of natural gas and 30 billion barrels of crude oil buried underground in Alaska, with a current value of more than 2 trillion US dollars! On October 24, 1867, the United States and Denmark signed a treaty, and the United States purchased two islands, St. Thomas and St. John in the Danish Virgin Islands, for $7.5 million. In 1898, the United States launched the Spanish-American War, defeated Spain, and seized Cuba, Puerto Rico, Guam, and the Philippines from Spain. Cuba and the Philippines achieved independence in 1902 and 1946 respectively, while Puerto Rico and Guam are still under US rule. The United States also made Hawaii its colony in 1898. Previously, in August 1842, Britain, France and the United States signed a declaration recognizing Hawaii as a sovereign country. However, after defeating Spain, the United States also annexed this independent island nation in the Pacific. In addition to the above-mentioned islands, the United States also occupied some islands in the Pacific in 1899, such as East Samoa, Midway Island, and Wake Island. In 1903, the United States obtained the right to dig the Panama Canal and the privileges of the canal zone. In 1917, the United States acquired all of the Virgin Islands from Denmark for a transfer fee of US$25 million. Of the aforementioned territories, Alaska and Hawaii became the 49th and 50th states of the United States respectively in 1959.