Mercer Island’s post office opened in 1924, and 2 of its places are on the National Register
More historic than 23% of U.S. towns · #163 of 285 in Washington. What drives it
Most of Mercer Island was built recently: 3% of its homes predate 1940 and the median home dates from 1973. Its Register listings are the Lakeview School and the Keewaydin Clubhouse. Below: maps from 1950 on and the census since 1970.
The Mercer Island post office opened in 1924, the earliest record of the town by name. Another post office, East Seattle (1904), opened inside today’s city and later closed.
First census: 19,047 in 19702020 census: 25,748102 years
How historic is Mercer Island?
C−
More historic than 23% of U.S. towns, on its age, its old homes and the National Register.
Founding year: the first Mercer Island post office (Blevins & Helbock, CC0).The full story ↓
History grade
What drives Mercer Island’s History grade
On its age, its old homes and the National Register, Mercer Island is more historic than 23% of U.S. towns, #163 of 285 in Washington. Its National Register listings hold the grade up; its age pulls it down.
C−
HistoryA character grade: shown, never part of Mercer Island’s overall grade.
Few Washington towns list much on the Register (a typical Washington town has 0.1 per 10,000 residents, the U.S. 2.4), so Mercer Island’s 1.2 sits near the middle of its state (62% of Washington towns have fewer) while its 3 historic buildings outnumber those of 65% of U.S. towns.
How sure. Graded on any two of the three inputs instead, the letter would range from D to C+. The pre-1940 share (±1.2 points) is firm at this size. The founding year is the first post office, not a stated founding date.
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 →
What stands out about Mercer Island’s past
Read from the archive, the National Register and the record. The page puts what stands out first.
The western side of the island was home to two Snoqualmie settlements prior to the 19th-century arrival of European American settlers in the Puget Sound region. Mercer Island was named for a member of the Mercer family of Seattle by 1860; Thomas Mercer, Aaron Mercer, and Asa Mercer, members of the Mercer family from Virginia, often rowed between the island and Seattle to pick berries, hunt, and fish. The first non-indigenous people to permanently settle on the island, Charles and Agnes Olds, arrived in 1885 and were followed by 15 other families within five years. The first large community, East Seattle, was toward the northwest side of the island—near the McGilvara neighborhood. Charles C. Calkins created the settlement in 1887 and later built a large and gilded resort, the Calkins Hotel. The hotel was reached via a steamboat ferry between Madison Park, Leschi Park, and the Eastside. G…
Every edition of the U.S. Geological Survey’s map of Mercer Island. Tap a year, or press play to watch the town change.
1950Mercer Island sheet · 1:24,000
U.S. Geological Survey historical topographic maps (public domain), via Esri’s collection of the scans. The red ring marks the center of Mercer Island.
On the National Register
2 historic places in Mercer Island
The country’s official list of buildings and places worth saving.
The Mercer Island post office opened in 1924, the earliest record of the town by name (U.S. post office records).
How does Mercer Island rank for history?
Mercer Island is more historic than 23% of U.S. towns, #163 of 285 in Washington. 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.
What is on the National Register in Mercer Island?
Two places: the Lakeview School (listed 1988) and the Keewaydin Clubhouse (2005).
How old are the homes in Mercer Island?
3% of Mercer Island’s homes were built before 1940 (Census estimate, ±1.2 points), against a typical 4.3% for a Washington town; the median home was built in 1973.
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 National Register of Historic Places (2), Wikipedia, Wikidata and Wikipedia for famous people, U.S. Geological Survey historical maps, U.S. Census counts (via Wikipedia), 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.
