On its age, its old homes and the National Register, Heidelberg Township is more historic than 74% of U.S. towns, #411 of 1,035 in Pennsylvania. All 2 inputs are above most U.S. towns; its share of homes from before 1940 ranks highest and its National Register listings lowest.
B+
HistoryA character grade: shown, never part of Heidelberg Township’s overall grade.
Pennsylvania towns list about as much on the Register as the country (a typical Pennsylvania town has 2.1 per 10,000 residents, the U.S. 2.4), so Heidelberg Township’s 3.0 sits near the middle of its state (61% of Pennsylvania towns have fewer) while its 1 listings outnumber those of 51% 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 is a Census survey estimate (±7.5 points).
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 Heidelberg Township’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 Heidelberg Township. Tap a year, or press play to watch the town change.
1902Slatington 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 Heidelberg Township.
The story so far
Heidelberg Township, in brief
Wikipedia doesn’t have a history of Heidelberg Township yet. The photos, dates and memories neighbors add here are how it gets written.
Heidelberg Township is a township in Lehigh County, Pennsylvania, United States. The population of Heidelberg Township was 3,416 at the 2010 census. It is a suburb of Allentown in the Lehigh Valley, which had a population of 861,899 and was the 68th-most populous metropolitan area in the U.S. as of the 2020 census.
Between the 2010 and 2020 censuses its population fell from 3,416 to 3,324 (-3%).
Intro from Wikipedia. Population: U.S. Census Bureau.
Timeline
Heidelberg Township, 1828 to 1955
Woven from the archive, old maps, post office records, the National Register and the people born here.
Heidelberg Township is more historic than 74% of U.S. towns, #411 of 1,035 in Pennsylvania. 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 Heidelberg Township?
One place: the Bridge in Heidelberg Township (listed 1988).
How old are the homes in Heidelberg Township?
22% of Heidelberg Township’s homes were built before 1940 (Census estimate, ±7.5 points), against a typical 18% for a Pennsylvania town; the median home was built in 1977.
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 (5), the National Register of Historic Places (1), U.S. Geological Survey historical maps, 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.
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