County research and study
New Castle County, Delaware
Use a county profile as a source-reading exercise or the geographic context for your own research. Keep the county FIPS identifier with your notes so that similarly named places in different states are not mixed.
Identify the right place
New Castle County is a county or county equivalent in Delaware. Its five-digit FIPS code is 10003; preserve the leading zero when storing county codes as text. The Gazetteer lists 67.69 square miles of water and a representative point at 39.575915, -75.644132. That point identifies the geography; it is not a street address or a site boundary.
Open this county in Census data · Download this county as JSON
County research and study checklist
- Write a specific research question before summarizing sources.
- Separate a Census estimate from an exact count or a current forecast.
- Cite the dataset and year next to every number in your notes.
The figures describe the county; they are not an evaluation of schools or an estimate of educational outcomes.
Sources and interpretation
Geography: 2025 U.S. Census Gazetteer. Population: Vintage 2025 estimates, July 1, 2025. County equivalents include parishes, boroughs, independent cities and planning regions. Puerto Rico population is not supplied by this population file.
Population is an estimate, not a live count. Gazetteer land and water measures describe the geographic area; they do not measure service availability, households, businesses or market demand. Match the FIPS code and source vintage when joining another dataset.
More county references in Delaware
- Kent County
Delaware · FIPS 10001
194,786 residents · 2025 estimate
- Sussex County
Delaware · FIPS 10005
277,140 residents · 2025 estimate