A. E. (Andrew Ellicott) Douglass (July 5, 1867 in Windsor, Vermont – March 20, 1962 in Tucson, Arizona) was an American astronomer.

During this time he was an assistant to Percival Lowell, but fell out with him when his experiments made him doubt the existence of artificial "canals" on Mars and visible spokes on Venus.

[5] On October 18, 1916, University President Rufus B. von KleinSmid announced that an anonymous donor had given the university US$60,000 "... to be used to buy a telescope of huge size"; the donor was later revealed to be Mrs. Lavinia Steward of Oracle, Arizona, a wealthy widow with an interest in astronomy and a desire to commemorate her late husband, Henry Steward.

After a couple of failed castings, the Spencer Lens Co. of Buffalo, New York produced the mirror for the Steward Telescope.

He can only dimly see which fact and which training will be of eminent use to him, but some special part of his education will take root in him and grow and pay for all of the effort which he and his friends have put into it.

Performing that same function, it has played a vast part in human history, and today it is telling us facts, forever wonderful, about the size of our universe; perhaps tomorrow it will give us practical help in showing us how to predict climatic conditions in the future.

Wissler, who had read about Douglass's work concerning the relationship between precipitation and tree growth, later contacted Douglass saying: Your work suggests to me a possible help in the archaeological investigation of the Southwest…We do not know how old these ruins are, but I should be glad to have an opinion from you as to whether it might be possible to connect up with your modern and dated trees specimens [with wood specimens] from these [prehistoric] ruins by correlating the curves of growth.

[8] On June 19, 1914, the curator of the American Museum of Natural History wrote a letter to Douglass expressing his desire to begin archaeological analysis as early as possible.

[8] In 1916 Douglass began obtaining and analyzing archaeological samples first collected during an expedition to northwest New Mexico by the University of Colorado and the American Museum of Natural History.

Douglass continued comparing samples between the two sites and concluded Pueblo Bonito actually predated Aztec Ruin by 40 to 45 years.

Although promising steps had been made in solving the mystery of the ruins in the Southwest, in 1920 the American Museum of Natural History discontinued funding Douglass's research.

Over 15 years after he began working with Clark Wissler, Douglass had bridged the gap and, as a result, had a continuous record of tree-ring data dating back to 700.

The chief was further pacified when Dr. Douglass' team placed pieces of turquoise in holes that were drilled into the logs to extract cores of wood.

This trade led to the discovery of one section of timber which revealed a very clear series of rings covering a period from 1260 to 1344.