The largest county-equivalent in District of Columbia
District of Columbia has one county-equivalent, so the question has one answer either way.
Sources: US Census Bureau, Population Estimates Program, Vintage 2025 Population Estimates, released 26 March 2026; US Census Bureau, Gazetteer Files, 2025 Gazetteer Files, released 10 September 2025. Retrieved 30 August 2026.
More on District of Columbia
Rebuilt from source data 30 August 2026. How these figures are produced.