Founding year: the first Rock Run Township post office (Blevins & Helbock, CC0).The full story ↓
History grade
What drives Rock Run Township’s History grade
On its age, its old homes and the National Register, Rock Run Township is more historic than 77% of U.S. towns. Its share of homes from before 1940 holds the grade up; its National Register listings pull it down.
A−
HistoryA character grade: shown, never part of Rock Run Township’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 Rock Run Township’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 any two of the three inputs instead, the letter would range from B− to A+. The pre-1940 share is a Census survey estimate (±12.7 points). 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 Rock Run Township’s past
Read from the archive, the National Register and the record. The page puts what stands out first.
The Norwegian-American Rock Run Settlement was established in 1839. Named after the town of Rock Run, it lay partly in Stephenson, partly in Winnebago County, Illinois.
Carnefix Mill, a three–story stone grist mill was built at Irish Grove 4 miles (6.4 km) south of Davis on Rock Run creek by George Raymer in the 1850s. The mill was still standing in 1970.
Davis Manufacturing Company Mill, built in Davis in 1876, was a 3+1⁄2-story stone flour mill with four run of stone powered by steam. The mill closed in 1880 and was demolished.
Every edition of the U.S. Geological Survey’s map of Rock Run Township. Tap a year, or press play to watch the town change.
1932Pecatonica 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 Rock Run Township.
Places that used to be
Old corners, places now gone and burying grounds
Old hamlets and crossroads still carry their names on the map.
The Rock Run Township post office opened in 1840, the earliest record of the town by name (U.S. post office records).
How does Rock Run Township rank for history?
Rock Run Township is more historic than 77% 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 Rock Run Township?
45% of Rock Run Township’s homes were built before 1940 (Census estimate, ±12.7 points), against a typical 11% for an Illinois town; the median home was built in 1952.
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 Wikipedia, U.S. Geological Survey historical maps 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.
