Joseph and Mary lived with their son Joseph, Jr. and his family in a small house while theirs was being built. Mary Priestley was primarily responsible for the design of the couple's new home and her family inheritance may have helped finance it, but she died before it was completed. By 1797, Joseph's laboratory was completed—the first part of the home to be finished. It was the first laboratory that "he had designed, built, and outfitted entirely himself" and was probably the first "scientifically-equipped laboratory" in the United States. Joseph continued his scientific and scholarly work in his new laboratory, identifying carbon monoxide (which he called "heavy inflammable air"). In 1798 Joseph Jr., his wife, and their children moved into the new house with Joseph Priestley. The house also held Priestley's library, which contained about 1600 volumes by his death in 1804 and was one of the largest in America at the time. The Priestley family held Unitarian church services in the drawing room and Joseph educated a group of young men until the local Northumberland Academy that he helped found was completed.