Steward has one of the few facilities in the world that can cast and figure the very large primary mirrors used in telescopes built in the early 21st century.

Steward Observatory owes its existence to the efforts of American astronomer and dendrochronologist Andrew Ellicott Douglass.

Over the next 10 years, all of Douglass’ efforts to secure funding from the University and the Arizona Territorial (and later State) Legislatures ended in failure.

After a couple of failed castings, the Spencer Lens Co. of Buffalo, New York ultimately produced a 36-inch mirror for the Steward Telescope.

In his dedication address, Douglass recounted the trials and tribulations of establishing the observatory, then gave the following eloquent justification for the scientific endeavor:[3] In concluding I wish to leave with you a more general view.

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.

Steward used to maintain a student observatory on Tumamoc Hill approximately 5 kilometers (3.1 mi) west of the campus, but that is no longer in operation.

The original observatory dome in Tucson now houses the Ray White Jr. 21-inch telescope and is used for public outreach and undergraduate education.

For the James Webb Space Telescope, Steward built the Near-Infrared Camera (NIRCam) and helped build the Mid-IR Instrument (MIRI).