The Missouri Compromise of 1820 staved off the slavery crisis for the time being, but by setting a line that excluded slave states above the parallel, it would also become incredibly contentious. It was against that backdrop and the election of Andrew Jackson that the Whigs emerged as opponents to the Jacksonian Democrats during a period of American history known as the Second Party System (1828-1854). Initially, the conflict was rooted not only in different visions for the United States - the Whigs believed in a strong central bank and federally funded infrastructure projects (known as “internal improvements”) - but also in opposition to one man: Andrew Jackson. When it first formed, the Democratic Party coalesced around Jackson, and his beliefs and actions became Democratic Party dogma, which left the diverse group of people who opposed Jackson to become the Whigs. The problem with this arrangement is that while the Whigs scored some notable successes as an opposition party, they found governing more difficult. The two Whigs elected president, William Henry Harrison and Zachary Taylor, died in office, raising to the presidency their respective vice-presidents, John Tyler and Millard Fillmore. Neither man succeeded in uniting the Whig Party behind him (a gargantuan task, to be sure), and neither was ever elected president in his own right. The increasing rancor over slavery is what finally killed the Whig Party. A truly national party, there were both Southern and Northern Whigs. When the Mexican-American War resulted in the country gaining millions of acres of land for potential new states, it galvanized both pro- and anti-slavery forces, and the Whig Party found itself incapable of navigating this fraught political issue before it eventually collapsed in the mid-1850s. However, many of its policy objectives, including a strong protective tariff, were picked up by the newly formed Republican Party moving forward.