Half of Boulder Hill’s homes were built after 1971
More historic than 10% of U.S. towns · #727 of 768 in Illinois. What drives it
Most of Boulder Hill was built recently: 1% of its homes predate 1940 and the median home dates from 1971. Below: maps from 1925 on and the census since 2000.
On its age, its old homes and the National Register, Boulder Hill is more historic than 10% of U.S. towns, #727 of 768 in Illinois. Its National Register listings hold the grade up; its share of homes from before 1940 pulls it down.
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HistoryA character grade: shown, never part of Boulder Hill’s overall grade.
Few Illinois towns list much on the Register (a typical Illinois town has 0.5 per 10,000 residents, the U.S. 2.4), so Boulder Hill’s 0.0 sits below most of its state (28% of Illinois towns have fewer) while its 0 listings outnumber those of 23% of U.S. towns.
How sure. Graded on two of the three inputs, so a change in either one moves the letter more than it would with three. The pre-1940 share (±1.3 points) is firm at this size.
Founding year: our sources. 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 Boulder Hill’s past
Read from the archive, the National Register and the record. The page puts what stands out first.
Every edition of the U.S. Geological Survey’s map of Boulder Hill. Tap a year, or press play to watch the town change.
1925Yorkville sheet · 1:62,500
U.S. Geological Survey historical topographic maps (public domain), via Esri’s collection of the scans. The red ring marks the center of Boulder Hill.
The story so far
Boulder Hill, in brief
Wikipedia doesn’t have a history of Boulder Hill yet. The photos, dates and memories neighbors add here are how it gets written.
Boulder Hill is a census-designated place (CDP) in Oswego Township, Kendall County, Illinois, United States. According to the 2020 census, the population was 8,394. It is part of the Chicago metropolitan area on the Fox River, south of Aurora.
Between the 2010 and 2020 censuses its population grew from 8,108 to 8,394 (+4%).
Intro from Wikipedia. Population: U.S. Census Bureau.
By decade
No old photos in the archives yet
Weddings on Main Street, storms, parades, school pictures, the old store. If it’s in your family album, it belongs here.
Be the first to add onePhotograph a print flat, in daylight, no flash.
Boulder Hill is more historic than 10% of U.S. towns, #727 of 768 in Illinois. 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 Boulder Hill?
1% of Boulder Hill’s homes were built before 1940 (Census estimate, ±1.3 points), against a typical 11% for an Illinois town; the median home was built in 1971.
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 U.S. Geological Survey historical maps and U.S. Census counts (via Wikipedia). Archive images are copied here with their credits and licenses, shown on each photo’s page. Refreshed monthly.
