Priestley was also politically involved. He was a supporter of both the American and French Revolutions. He saw them as the beginning of Armageddon, as foretold in the Bible. These views, which he made no effort to hide, were considered seditious, or traitorous, by English authorities and his neighbors. In 1791, a mob destroyed his house and laboratory in Birmingham because of his preaching that Armageddon was coming, and support of the revolutions.
This riot, along with growing threats and dangers, pushed him to decide to immigrate to the United States. With his sons he planned to set up a model community on undeveloped land in Pennsylvania, but that didn’t happen. He and his wife did, however, build a beautiful home with its own laboratory far up the Susquehanna River in Northumberland, Pennsylvania.