William Slade Jr. was an American Whig and Anti-Masonic politician. He served as a U.S. Representative from Vermont from 1831 to 1843, where he was an outspoken opponent of slavery. He was the 17th governor of Vermont.

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 disappeared after 1838.