Joseph Priestley (1733-1804) was the founder of modern chemistry and discoverer of oxygen, a theologian, and political philosopher. He came to Pennsylvania in 1794 after suffering persecution in his homeland, England, for his dissenting religious beliefs and liberal political views. Northumberland became his home for the last 10 years of his life. His Federal-style house features a laboratory and period objects, and a visitor centre includes exhibits that focus on his varied accomplishments.