Please briefly describe the "Westward Movement"

After the independence of the United States, the British government's decree prohibiting immigrants from moving westward was abolished, and many immigrants from the eastern coastal areas and Europe crossed the Appalachian mountains and flocked to the west. According to statistics, the population west of Appalachia accounted for only 1/7 of the total population of the United States in 18 10, and increased to 1/4 after 10. Among these immigrants, there are both slave owners in the south and land speculators in the north; However, the largest number of poor pioneers-hunters, miners, herders and farmers-came to the west to make a living and became the main body of early immigrants in the west. The westward movement has three climaxes. The first time was from the end of 18 to the beginning of 19. At that time, the United States bought Louisiana from France, and a large number of immigrants flocked to the west to open up Ohio, Kentucky and Tennessee, laying the foundation for the growing grain-producing areas in the central and western regions. The second time is after 18 15. Later, the immigrants opened up in the Great Lakes region, established the bases of grain production and animal husbandry in the United States, and established cotton plantations in the plain area between southern Georgia and Louisiana near the Gulf of Mexico in the south, expanding the slave plantation economy in the south. The third climax was in the middle of19th century, which opened Oregon and California. By 1890, the westward movement officially ended. The westward movement and territorial expansion are intertwined. In the westward movement, the western region was developed, which greatly promoted the economic development of the United States. However, with the westward movement, a large number of Indians were slaughtered, and the survivors were forcibly driven to a more desolate "reservation". Their forced migration road is also known as the "tears road" of Indians.