Following his service with the Indian Peace Commission, Tappan worked for his former associate Henry Villard at the Oregon Steamship and Railway Company during the 1870s to help systematize and encourage emigration to Oregon. He traveled during this time to Alaska and also represented Oregon at the Centennial Exposition in 1876 in Philadelphia. He later lived in California for a time. Tappan was appointed during the Presidency of Chester A. Arthur to become the first superintendent of the United States Indian Industrial School in Genoa, Nebraska, in 1884–1885. The school was started to teach trades and educate Native Americans. Tappan served until removed by President Grover Cleveland.
