On August 6, 1885, Sheldon got married. She married a man named Earl Barnes. She met him when he was a student of hers, and he was 11 years younger than her. He became the head of the education department at Stanford University in 1981. Sheldon moved with him and also worked at Stanford. She researched and taught classes about the History of Europe and the Pacific Slope areas. Sheldon and Barnes wrote a book together in 1891. It was called "Studies in American History." They also wrote another book in 1896, together. She wrote another book of her own, too. It was called "Studies of Historical Method," and taught readers about historical method. In 1897, Sheldon and Barnes quit working at Stanford. They traveled to Europe and wrote while they were there.