Llenroc
Why it's listed
Llenroc is a stone mansion on a grassy knoll at 100 Cornell Avenue in Ithaca, overlooking Cayuga Lake. Designed in 1865 for Ezra Cornell, it took nearly ten years to complete. The house is built of smooth-faced Ithaca limestone with gray Onondaga limestone trim, and its steep gables, jerkin-headed dormers, slate roof and carved details express the Gothic Revival style. German stonecutters were brought in, and Cornell oversaw much of the construction himself while also building the first buildings of the university he founded. Inside, black walnut and oak woodwork, marble fireplaces, a carved three-flight staircase and an ornate dining room survive. The nomination describes it as the last extant building linked to Cornell's personal life and as Ithaca's finest post-Civil War Gothic residence. The Delta Phi fraternity chapter that owns and occupies it has preserved its character, and both the exterior and principal rooms remain virtually unchanged.
Significance in brief: The nomination calls Llenroc the last surviving building tied to the personal life of Ezra Cornell, founder of Cornell University. It is described as Ithaca's finest post-Civil War Gothic residence and an exceptionally well-preserved example of high style masonry Gothic Revival architecture, with outstanding craftsmanship supervised by Cornell himself.
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 80002781, listed April 16, 1980. Summary generated October 2026 (model claude-sonnet-5-5, prompt v1.0-2026-10-29, confidence high).
Key facts
| Address | 100 Cornell Ave., Ithaca |
|---|---|
| County | Tompkins County |
| Listed | April 16, 1980 |
| Reference number | 80002781 |
| Resource type | Building |
| Period of significance | 1865-1875 |
| Architect / builder | Nichols and Brown |
| Architectural style | Gothic Revival |
| Areas of significance | Industry, Education, Architecture, Social History, Invention |
| Level of significance | National |
| Status (as stated in the nomination) | Owned and occupied by the Pi chapter of Delta Phi fraternity; exterior and principal rooms described as virtually unchanged, with kitchen, pantries, basement and third floor adapted for fraternity use. |
| Acreage | 2.9 |
| Coordinates | 42.44678, -76.49190 (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 80002781.
- Nomination form (PDF, National Archives) — catalog entry
- Wikipedia article (used for cross-checking only; text not reproduced here)
- Wikidata Q6662005
- This listing as JSON
Last updated October 2026. Found an error? See the editorial policy for how to report it.