Each edition grades its towns against each other only.
More historic than 28% of U.S. towns · #112 of 140 in Iowa. What drives it
Below: maps from 1916 on and the census since 1880.
The Rock Valley post office opened in 1879, the earliest record of the town by name. Another post office, Rock Mills (1877), opened inside today’s city and later closed.
More historic than 28% of U.S. towns, on its age, its old homes and the National Register.
On its age, its old homes and the National Register, Rock Valley is more historic than 28% of U.S. towns, #112 of 140 in Iowa. Its share of homes from before 1940 holds the grade up; its National Register listings pull it down.
Iowa towns list more on the Register than most of the country (a typical Iowa town has 9.1 per 10,000 residents, the U.S. 2.4), so Rock Valley’s 0.0 sits below most of its state (17% of Iowa 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 →
Read from the archive, the National Register and the record. The page puts what stands out first.
The first neighbors to add old photos shape how Rock Valley’s history is told.
From Wikipedia’s history of Rock Valley.
The town of Rock Valley was platted in 1879 by a Colonel Ira Warren, a Civil War veteran, and the Chicago Milwaukee & St. Paul Railway on ground owned by Warren.
Text from Wikipedia, licensed CC BY-SA 4.0.
Woven from the archive, old maps, post office records, the National Register and the people born here.
On the mapFirst mapped by the U.S. Geological SurveyEvery edition of the U.S. Geological Survey’s map of Rock Valley. Tap a year, or press play to watch the town change.
U.S. Geological Survey historical topographic maps (public domain), via Esri’s collection of the scans. The red ring marks the center of Rock Valley.
Fire insurance maps drew every building, what it was made of and what it was used for, so insurers could price the risk of fire. Pick a sheet.
1916Sheet 1 of 1Sanborn Map Company, via the Library of Congress. Editions published in 1930 or earlier, which are in the public domain.
Grew from 100 people in 1880 to 4,059 in 2020, more than tenfold.
15 censuses, 1880–2020.
U.S. Census Bureau decennial counts, from the census table on Rock Valley’s Wikipedia page.
Writers, athletes, leaders and more, ranked by how widely they’re known.
Rock Valley’s post office has been open since 1879. Another post office, Rock Mills, 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).
The Rock Valley post office opened in 1879, the earliest record of the town by name (U.S. post office records).
Rock Valley is more historic than 28% of U.S. towns, #112 of 140 in Iowa. 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.
12% of Rock Valley’s homes were built before 1940 (Census estimate, ±7.7 points), against a typical 22% for an Iowa town; the median home was built in 1983.
What the archives can’t tell you, neighbors can.
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 Wikimedia Commons (1), 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), the USGS Geographic Names Information System and Sanborn fire insurance maps (Library of Congress). Archive images are copied here with their credits and licenses, shown on each photo’s page. Refreshed monthly.
2004