The Anti-Masonic Party was the earliest third party in the United States. Formally a single-issue party, it strongly opposed Freemasonry in the United States. It was active from the late 1820s, especially in the Northeast, and later attempted to become a major party by expanding its platform to take positions on other issues. It declined quickly after 1832 as most members joined the new Whig Party; it dissolved after 1838.
The party was founded following the disappearance of William Morgan, a former Mason who had become a prominent critic of the Masonic organization. Many believed that Masons had murdered Morgan for speaking out against Masonry and subsequently many churches and other groups condemned Masonry.