PLACE / TIME / EVIDENCE
Same place.
Different county.
Follow Illinois’s changing county lines. Find the jurisdiction, read what changed, and choose your next place to research.
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View cropped to modern Illinois. Historical counties sometimes extended beyond this frame. Shapes are generalized, not property boundaries. NCA = non-county area. Labels thin automatically to reduce overlap.
THE PAPER TRAIL
County chronology
Includes organization and attachment events that may not change the drawn boundary.
SOURCE NOTES
A map is a starting point.
Historical evidence
Gordon DenBoer, historical compiler, Illinois Atlas of Historical County Boundaries, edited by John H. Long; GIS specialist Laura Rico-Beck and the Newberry atlas team. Newberry Library, 2008. Coverage: December 9, 1778 through December 31, 2000. Event descriptions and citations are retained from the dataset.
Open Newberry’s Illinois atlas ↗ · Bibliography ↗ · Historical commentary ↗
What the lines cannot tell you
A county could exist before it operated independently. Read its dated attachment and organization notes. A historical jurisdiction does not establish which repository holds a record today.
The map represents the atlas’s colonial, territorial and state administrative claims. It is not a map of Indigenous nations, land ownership or a complete account of sovereignty.
Modern comparison: U.S. Census Bureau, 2024 generalized counties ↗. This is a dated reference layer, not a verified 2026 boundary survey.
Data treatment, exceptions and reuse
Historical polygons are clipped to the modern Illinois footprint and simplified to 0.001 degrees for display. Coordinates are plotted at an Illinois overview scale; no invalid source geometries required repair during conversion. Original downloaded files are retained separately. Near-boundary questions require the source descriptions and more detailed maps.
The downloaded Illinois package contains 369 historical polygon versions and 538 chronology entries. Its commentary explains interpretive decisions, including early territorial jurisdictions. Organization and attachment events may appear in the chronology without changing the drawn boundary.
Newberry’s current reuse statement specifies CC0. Its download page says older license notices included in the files are superseded. Reviewed October 30, 2026. No claim is made that Brick Wall Protocol independently rechecked every cited law.