Hale Solar Laboratory
Also known as: Hale Laboratory
Why it's listed
Built in 1924-25 on a 95 by 300 foot lot in Pasadena, the Hale Solar Laboratory is a T-shaped reinforced concrete building in Spanish Colonial Revival style, with mission tile roofing, roughly plastered walls and deep-set windows. Johnson, Kaufman, and Coate designed it for astronomer George Ellery Hale, who had retired from directing Mount Wilson Observatory. A domed telescope tower rises 30 feet and sits above a 78-foot well leading to a basement spectrograph room. Sculptor Lee Lawrie created two bas-reliefs, and Beatrix Farrand designed the landscaping. Hale used the laboratory in his later years to study the sun, redesigning the spectroheliograph into the spectrohelioscope to observe solar prominences in hydrogen light. After his death in 1938 it continued as a solar observatory, and in 1952 the Babcocks built the first solar magnetograph there. The building remains unaltered, with much of Hale's equipment and library still inside.
Significance in brief: The nomination argues the building is significant for its association with its owner-builder George Ellery Hale, an internationally famous astronomer who founded major observatories and helped organize Caltech and the Huntington Library. It was also the site of important solar research, including Hale's refinement of the spectrohelioscope and the first solar magnetograph built in 1952.
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 86000103, listed January 23, 1986. Summary generated October 2026 (model claude-sonnet-5-5, prompt v1.0-2026-10-29, confidence high).
Key facts
| Address | 740 Holladay Rd., Pasadena |
|---|---|
| County | Los Angeles County |
| Listed | January 23, 1986 |
| Reference number | 86000103 |
| Resource type | Building |
| Period of significance | 1924-1952 |
| Architect / builder | Johnson, Kaufman, Coate |
| Architectural style | Spanish Colonial Revival |
| Criteria |
|
| Areas of significance | Science, Architecture, Invention |
| Level of significance | National |
| National Historic Landmark | Yes, designated December 20, 1989 |
| Status (as stated in the nomination) | Described as unaltered since 1924 and in excellent condition, retaining much of the original equipment and Hale's books and journals. It currently houses offices of the Mount Wilson Institute, and a private residence was built on the grounds. |
| Acreage | 0.7 |
| Coordinates | 34.13326, -118.12125 (NPS GIS) |
What listing means for this property
National Register listing is honorary: it recognises significance and does not restrict what a private owner may do without federal money or permits. It unlocks the 20% federal rehabilitation tax credit for income-producing buildings, state credits in many states, and Section 106 review when federal agencies are involved. See what listing means in practice.
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 86000103.
- Nomination form (PDF, National Archives) — catalog entry
- Wikipedia article (used for cross-checking only; text not reproduced here)
- Wikidata Q5641417
- This listing as JSON
Last updated October 2026. Found an error? See the editorial policy for how to report it.