Hint: The United States of America was created on July 4 1776, when thirteen British colonies were declared independent in North America.
Complete answer: The first expansion of the country came with the purchase of Louisiana in 1803 which almost doubled the country’s territory, although there was disagreement in the southeastern border with Spanish Florida. Oregon country in 1821 provided the United States access to the pacific ocean but for a certain amount of time, it was shared with the United Kingdom. With the annexation of the Republic of Texas in 1845, it led to Mexican - American War, in which the United States emerged victoriously and captured the northern part of Mexico including the state of California. The cultural beliefs of the United States American dwellers provided a strong impetus for westward expansion in the 19th century. The country’s expansion beyond the northern area began in 1856 with Guano Island Acts but economically important was the acquisition of islands in the Pacific Ocean and the Caribbean Sea. Louisiana, Missouri, Nevada and Pennsylvania expanded significantly by acquiring additional territory. The last state of the contiguous United States which was commonly known as the ‘’lower 48’’ was admitted in 1912 and the fifteenth and the most recent was admitted in 1959.
Therefore, option E is the correct answer.
Note: The philosophy was the main reason for the U.S. territorial expansion and also justified the removal of Native Americans and other people from their homes. The rapid expansion intensified the issue of slavery as new states were added all of which led to the outbreak of the Civil War.