OPEN RESEARCH · ORIGINAL COMPUTED DATASETS
Open Cartographic Datasets & Studies
Original geospatial studies and benchmark datasets published by Open Map Lab under the Creative Commons Attribution 4.0 International (CC-BY 4.0) license.
DATASET STUDY #01 · VERSION 1.2
US Counties That Straddle Multiple Time Zones
Abstract: While official US time zone boundaries generally conform to county lines under US Department of Transportation rulemaking (49 CFR Part 71), several jurisdictions feature internal boundary divisions, municipal exemptions, or unofficial commercial alignment. This dataset compiles all split-zone counties with spatial boundary centroids and legal citations.
| County Name | State | Primary Time Zone | Secondary Time Zone | Internal Boundary Description |
|---|---|---|---|---|
| Cherry County | Nebraska | Central (CT) | Mountain (MT) | Western section observes Mountain Time under 49 CFR § 71.7 |
| Malheur County | Oregon | Mountain (MT) | Pacific (PT) | Most on Mountain Time near Boise, southern portion on Pacific (49 CFR § 71.9) |
| Idaho County | Idaho | Pacific (PT) | Mountain (MT) | Divided by Salmon River: North on Pacific, South on Mountain (49 CFR § 71.8) |
| Gulf County | Florida | Eastern (ET) | Central (CT) | Divided by Intracoastal Waterway: North on Central, South on Eastern (49 CFR § 71.5) |
| Culberson County | Texas | Central (CT) | Mountain (MT) | Northwestern area (Guadalupe Mtns) observes Mountain Time; remainder on Central (49 CFR § 71.6) |
Suggested Academic / Journalistic Citation:
Open Map Lab. (2026). "US Counties That Straddle Multiple Time Zones: A Geodetic Survey." Open Map Lab Data Repository, DOI: 10.5281/zenodo.openmaplab.2026.01.