Astronomer remembered for establishing a wood ring-dating methodology called dendrochronology. He also researched the relationship between the solar cycle and the formation of tree rings.
During the 1890s, he worked at the Lowell Observatory in Flagstaff, Arizona.
Several Mars and Moon craters were named after him.
He was born Andrew Ellicott Douglass in Windsor, Vermont. He later settled in Tucson, Arizona.
He began his scientific career as an assistant to renowned astronomer Percival Lowell.