Marconi Wireless-Synanon Tomales Bay Headquarters Historic District (Boundary Increase)
Also known as: Marconi Property
No coordinates published for this listing.
Why it's listed
Four buildings on the east shore of Tomales Bay in Marshall, California, survive from Station KPH, a wireless receiving station built in 1913 by the J.G. White Engineering Company for the Marconi Wireless Telegraph Company of America. They are a two-story hotel for operators and guests, a powerhouse, and two cottages for the station's managers. All are steel-frame and concrete buildings with red tile roofs. The hotel has a long veranda on 35 concrete pillars and stone fireplaces in the lobby and billiard room. Dedicated in 1914, the station worked with a transmitter at Bolinas to open dependable communication between California and Hawaii, and onward to Japan, and it also served ships across the Pacific. The Navy took it over in 1917, and the Radio Corporation of America operated it from 1920 until radio work moved to Point Reyes in 1931. The nominated parcel excludes the original operating building and later buildings constructed during Synanon's 1965 to 1980 occupancy.
Significance in brief: The station was the receiving half, paired with a transmitter at Bolinas, of the first dependable wireless link between the continental United States and Hawaii, and through Hawaii to Japan. It also provided ship-to-shore service across the Pacific. The form argues national significance for its role in starting trans-Pacific radio communication.
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 100011433, listed January 31, 2025. Summary generated October 2026 (model claude-sonnet-5-5, prompt v1.0-2026-10-29, confidence medium).
Key facts
| Address | 18500 CA 1, Marshall |
|---|---|
| County | Marin County |
| Listed | January 31, 2025 |
| Reference number | 100011433 |
| Resource type | District |
| Period of significance | 1914-1931 |
| Architect / builder | J.G. White Engineering Company of New York City (listed on the form as J.C. White, Engineering Company) |
| Architectural style | Late 19th and 20th Century Revivals |
| Criteria |
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| Areas of significance | Communications |
| Level of significance | National |
| Status (as stated in the nomination) | Rehabilitation for use as a non-profit conference center was under way when the form was prepared; the roofs were described as in good condition and the exteriors largely unchanged. |
| Acreage | 62.29 |
What listing means for this property
This is a historic district. Buildings within its boundary are either contributing (they add to the district's significance) or non-contributing. Owners of contributing income-producing buildings can claim the 20% federal rehabilitation tax credit; homeowners should look at state credits. National Register districts impose no design review by themselves; a local historic district ordinance, if one exists, does (the difference explained).
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 100011433.
- Nomination form (PDF, National Archives) — catalog entry
- This listing as JSON
Last updated October 2026. Found an error? See the editorial policy for how to report it.