University of Illinois Astronomical Observatory
Why it's listed
Built in 1896 on the University of Illinois campus in Urbana, this small brick observatory was designed by architect Charles A. Gunn and built by Bevis and Company. It has a T-shaped plan, buff Roman brick walls, limestone sills and lintels, and a round tower holding a dome and a twelve-inch Warner and Swasey refractor telescope. Between 1907 and 1922, director Joel Stebbins, physics instructor F.C. Brown and physics professor Jacob Kunz used that telescope to develop first the selenium cell and then the alkali-metal photoelectric cell for measuring starlight. Their work replaced visual and photographic estimates of stellar brightness with precise electrical measurement, which became the standard method in astronomy. Additions from 1956 and 1966 enlarged the building, but the tower, equatorial room, dome, pier and telescope remain original. The observatory is still used for teaching, though it needs repairs to its deck, cornice and dome.
Significance in brief: The observatory is where Joel Stebbins, working with F.C. Brown and Jacob Kunz, developed the selenium cell and photoelectric cell for astronomical photometry between 1907 and 1922. This work made photoelectric measurement of stellar magnitudes the standard technique. The building keeps its original tower, equatorial room, dome, pier and twelve-inch Warner and Swasey refractor.
Machine-generated summary. This summary was generated by a language model from the official nomination document and has not been reviewed line by line by an editor. It may contain errors. Check the source document before relying on any detail. Source: nomination document (PDF) · National Archives catalog entry. NRHP reference 86003155, listed November 6, 1986. Summary generated October 2026 (model claude-sonnet-5-5, prompt v1.0-2026-10-29, confidence medium).
Key facts
| Address | 901 S. Mathews Ave., Urbana |
|---|---|
| County | Champaign County |
| Listed | November 6, 1986 |
| Reference number | 86003155 |
| Resource type | Building |
| Period of significance | 1900-1922 (specific dates 1907-1922) |
| Architect / builder | C.A. Gunn, architect; Bevis & Co., contractors |
| Areas of significance | Science |
| Level of significance | National |
| Status (as stated in the nomination) | Occupied and still used as a teaching observatory. Additions were built in 1956 and 1966. The building is structurally sound but has suffered from deferred maintenance, including a deteriorating observation deck, cornice and dome surface, and water damage in the equatorial room. |
| Acreage | 0.9 |
| Coordinates | 40.10502, -88.22623 (NPS GIS) |
What listing means for this property
For a publicly owned building or structure, listing mainly matters when federal funds, permits or licences are involved: projects then go through Section 106 review so effects on the property are considered. Listing also strengthens applications for preservation grants and, for leased income-producing uses, can enable the federal rehabilitation tax credit.
General information, not legal or tax advice. Rules change; confirm with your State Historic Preservation Office or a qualified adviser.
Sources and further reading
- National Park Service, National Register of Historic Places database (snapshot May 2026), reference 86003155.
- Nomination form (PDF, National Archives) — catalog entry
- Wikipedia article (used for cross-checking only; text not reproduced here)
- Wikidata Q3348346
- This listing as JSON
Last updated October 2026. Found an error? See the editorial policy for how to report it.