American imperialism began in the early 19th century, but many Americans had different opinions about whether imperialism was proper and legal. Many Americans at the turn of the century believed that bringing new nations to the United States was necessary to improve America. Legally, imperialism has violated the Constitution and contradicted the statements contained in the Declaration of Independence and Washington's Farewell Address. American imperialism was deemed appropriate because it involved the idea of ​​social Darwinism and helped improve American industries. The need to obtain land to increase trade and materials led many countries, such as England, France, and Germany, to take control of much of Africa and Asia for industrial reasons. After the American frontier was officially closed according to the 1890 census, the push for American imperialism increased to expand American opportunities. The Spanish-American War of 1898 also led to American imperialism. Spain's defeat left Guam, Puerto Rico, Cuba, and the Philippines to the United States. Most Americans during the late 19th century were Anglo-Saxon Christians who believed in Social Darwinism, or the idea of ​​“survival of the fittest.” This led many Americans to want to Americanize the Spanish territories they obtained. The United States had also annexed Hawaii in 1898, which caused many Americans to question American imperialism. Groups such as the Anti-Imperialist League led the debate on whether imperialism was correct and legal. American imperialism in the early 20th century was appropriate because it helped American industry and went along with the popular idea of ​​social Darwinism, but it was not legitimate because it went against the Constitution and did not agree with the views of America's founding fathers on foreign interactions..