Johnson County, Indiana
county in Indiana, United States
Johnson County is a county located in the U.S. state of Indiana. As of 2020, the population was 161,765. The county seat is Franklin. Johnson County is included in the Indianapolis-Carmel-Anderson, IN Metropolitan Statistical Area.
Transportation
Transit
Access Johnson County
Major highways
Interstate 65
Interstate 69
U.S. Route 31
State Road 44
State Road 135
State Road 144
State Road 252
Airport
KHFY - Greenwood Municipal Airport
3FK - Franklin Flying Field
Geography
According to the 2010 census, the county has a total area of 321.79 square miles (833.4 km2), of which 320.43 square miles (829.9 km2) (or 99.58%) is land and 1.36 square miles (3.5 km2) (or 0.42%) is water.
Adjacent counties
Marion County (north)
Shelby County (east)
Bartholomew County (southeast)
Brown County (southwest)
Morgan County (west)
History
Johnson County was formed in 1823. It was named for John Johnson, a Justice of the Indiana Supreme Court. This is probably John Johnson of Knox County, delegate to the State constitutional convention, appointed to the Supreme Court in 1816.
Cities and towns
Bargersville
Edinburgh (part)
Franklin
Greenwood
New Whiteland
Princes Lakes
Trafalgar
Whiteland
Extinct
Farwest
Townships
Blue River
Clark
Franklin-Union-Needham, which merged in January 2022
Hensley
Nineveh
Pleasant
White River
The south end of the county is also home to the Camp Atterbury military installation.
Climate and weather
In recent years, average temperatures in Franklin have ranged from a low of 21 °F (−6 °C) in January to a high of 86 °F (30 °C) in July, although a record low of −22 °F (−30 °C) was recorded in January 1985 and a record high of 104 °F (40 °C) was recorded in June 1988.
Begin with the source’s own compact description: “Johnson County, Indiana” is county in Indiana, United States. The dossier treats that line as a proposition to test through Johnson, County and Indiana, not as a finished interpretation.
Why this record matters
The phrase “county in Indiana, United States” supplies a clear boundary for inquiry. It also exposes the unanswered questions: who defined that boundary, when it became stable and which sources sit outside it.
Place names and jurisdictional language are key evidence: both can reveal earlier catalogue descriptions and overlooked record series. The source revision retrieved here is dated Sep 17, 2026. The linked authority identifier is Q506563. VIAF identifies the subject as 138363483. The Library of Congress control number is n79085123. Authority coordinates are 39.490, -86.100. 5 of 5 selected statements include explicit references; 1 carry qualifiers and 0 use preferred rank. The first chronological checks are 2020, 2010, 1823 and 1816.
Modern boundaries and familiar names can conceal earlier jurisdictions or structures that do not align with the present site. The source lead contains qualifying language; that uncertainty should survive quotation, summary and reuse. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
How to read it
Treat names, boundaries and functions as historically changeable. Maps, plans, inventories and administrative records can clarify what the place meant at different dates.
- Historic place names
- Jurisdictional context
- Routes into maps and plans
Contemporary maps, plans, listed-building records, estate papers and the responsible local or national archive.
Three-step research path
- Establish the record: confirm the title “Johnson County, Indiana”, its source revision and the description used here.
- Expand the search: follow Johnson County, Indiana primary sources, Johnson County, Indiana archive and Johnson research across catalogues and specialist indexes.
- Test the account: compare the strongest cited source with the responsible institution’s current record and note any disagreement.
Questions for further research
- Which source most directly establishes the central claim about “Johnson County, Indiana”?
- Which earlier names or jurisdictions may reveal additional records?
- Which authority defined the place, boundary or structure at the relevant date?
Search terms from this dossier
This entry incorporates text from “Johnson County, Indiana” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.