This chapter begins by examining the James Monroe and John Quincy Adams administrations. They continued America’s expansionist drive and the quest for security. John Quincy Adams was one of America’s first grand strategists, and he and Monroe used Andrew Jackson to secure parts of Florida from Spain while also giving us the Monroe Doctrine, which meant the US wouldn’t tolerate establishment of any European footholds in the Western hemisphere. They also fought the First Seminole War. Andrew Jackson succeeded Adams as president. Achieving security against enemies foreign and domestic was his key aim. He fought against the Bank of the United States, pursued Indian Removal that famously produced the “Trail of Tears,” quashed the Nullification Crisis, and fought wars against the Blackhawk, Creeks, and Seminole. The Martin Van Buren, William Henry Harrison, and John Tyler administrations are briefly examined on the way to the James K. Polk administration and the Mexican War. Polk’s victorious war, which included campaigns by Zachary Taylor and Winfield Scott, saw the US seize enormous tracts of Mexico, including California. Expansion was Polk’s aim. Expansionism became inextricably tied to Manifest Destiny in 1845.