Know what’s behind your map.

Open data, documented sources

The map library is stored with the application and served from the same origin. It uses a pinned Natural Earth repository snapshot and US Atlas county data. Dataset processing simplifies coordinates for browser performance; simplification can remove tiny details.

Natural Earth

Natural Earth datasets are in the public domain. This collection uses version 5.1.1 reference geometry from a pinned repository snapshot. Country geometry is generalised at 1:50m scale; regional geometry is derived from the 1:10m admin-1 layer. Administrative levels vary between countries and can reflect an older structure.

US counties

The US counties layer comes from US Atlas 3.0.1, based on 2017 Census geography. It has 3,231 county-equivalent features including territories. Falls Church is represented by a generalised line in this source and receives a selection marker in the editor. This is not a current official county boundary service.

Disputed boundaries and suitability

Names and boundaries reflect source conventions, not a position on sovereignty. For official, legal, election or time-sensitive work, verify the appropriate authority’s data. Use custom GeoJSON when a different geographic interpretation or vintage is required.

Download the machine-readable source manifest · Natural Earth terms · US Atlas source