Keaau’s post office opened in 1938
More historic than 14% of U.S. towns. What drives it
Most of Keaau was built recently: 7% of its homes predate 1940 and the median home dates from 1978.
How Keaau began
When was Keaau founded?
The Keaau post office opened in 1938, the earliest record of the town by name. Another post office, Olaa (1900), opened inside today’s town and later closed.
How historic is Keaau?
More historic than 14% of U.S. towns, on its age, its old homes and the National Register.
What drives Keaau’s History grade
On its age, its old homes and the National Register, Keaau is more historic than 14% of U.S. towns. Its share of homes from before 1940 holds the grade up; its age pulls it down.
Few Hawaii towns list much on the Register (a typical Hawaii town has 0.0 per 10,000 residents, the U.S. 2.4), so Keaau’s 0.0 sits below most of its state (28% of Hawaii towns have fewer) while its 0 listings outnumber those of 23% of U.S. towns.
Founding year: the first post office (other dates in Quick answers). Homes: Census ACS 2020–24. National Register: National Park Service, May 2026 list; each listing counted once (boundary changes and added documentation belong to their listing), and a historic district counts its contributing buildings. How TownRatings grades history →
Lost post offices, old corners and places now gone
Keaau’s post office has been open since 1938. Another post office, Olaa, opened and closed inside today’s town.
US Post Offices dataset (Blevins & Helbock, CC0). Places and cemeteries from the USGS Geographic Names Information System (2021).
History across the town line
Each neighbor’s History grade, on the same three inputs.
Questions about Keaau’s history
What year was Keaau founded?
The Keaau post office opened in 1938, the earliest record of the town by name (U.S. post office records).
How does Keaau rank for history?
Keaau is more historic than 14% of U.S. towns. The History grade combines the town’s founding era, the share of homes built before 1940 and its National Register listings. It’s a character grade, so it isn’t part of the overall grade. How it works.
How old are the homes in Keaau?
7% of Keaau’s homes were built before 1940 (Census estimate, ±5.0 points), against a typical 1.7% for a Hawaii town; the median home was built in 1978.
Memory lane
What the archives can’t tell you, neighbors can.
Where this page comes from
Founding dates: Wikidata, Wikipedia, the U.S. post office records of Blevins & Helbock (CC0) and the Census. Homes by year built: Census ACS 2020–24. National Register of Historic Places: National Park Service (list of May 22, 2026). Old photos, postcards and papers: Wikimedia Commons, the Library of Congress and other public archives, credited on each item’s page. Maps: U.S. Geological Survey historical topographic maps (via Esri) and Sanborn fire-insurance maps (Library of Congress). History text and census tables: Wikipedia (CC BY-SA 4.0). Places that used to be: USGS Geographic Names Information System (2021).
From the US Post Offices dataset (Blevins & Helbock) and the USGS Geographic Names Information System. Archive images are copied here with their credits and licenses, shown on each photo’s page. Refreshed monthly.