US counties that grew the most since 1990

Population growth in the US has clustered tightly in the Sun Belt and in the suburban ring of a handful of metros. Across 612 US counties with at least 100,000 residents today and a 1990 baseline, the 25 biggest absolute gainers are below.

Maricopa County, Arizona added +2,437,647 residents since 1990, the largest absolute gain of any county in the country.

#	Place	1990	Latest	Change
1	Maricopa County, Arizona	2,122,101	4,559,748	+2,437,647
2	Harris County, Texas	2,818,199	4,838,303	+2,020,104
3	Clark County, Nevada	741,459	2,329,548	+1,588,089
4	Riverside County, California	1,170,413	2,478,600	+1,308,187
5	Tarrant County, Texas	1,170,103	2,167,390	+997,287
6	Los Angeles County, California	8,863,164	9,808,667	+945,503
7	Collin County, Texas	264,036	1,163,337	+899,301
8	Bexar County, Texas	1,185,394	2,067,341	+881,947
9	Orange County, Florida	677,491	1,471,937	+794,446
10	San Diego County, California	2,498,016	3,288,774	+790,758
11	King County, Washington	1,507,319	2,287,171	+779,852
12	San Bernardino County, California	1,418,380	2,197,104	+778,724
13	Dallas County, Texas	1,852,810	2,621,179	+768,369
14	Wake County, North Carolina	423,380	1,178,653	+755,273
15	Orange County, California	2,410,556	3,165,820	+755,264
16	Travis County, Texas	576,407	1,330,015	+753,608
17	Broward County, Florida	1,255,488	1,977,129	+721,641
18	Denton County, Texas	273,525	979,561	+706,036
19	Hillsborough County, Florida	834,054	1,522,748	+688,694
20	Palm Beach County, Florida	863,518	1,533,806	+670,288
21	Fort Bend County, Texas	225,421	893,767	+668,346
22	Mecklenburg County, North Carolina	511,433	1,154,681	+643,248
23	Gwinnett County, Georgia	352,910	979,864	+626,954
24	Sacramento County, California	1,041,219	1,594,006	+552,787
25	Williamson County, Texas	139,551	672,688	+533,137

Key findings

• Maricopa County, Arizona leads the list at +2,437,647.
• The 25th-ranked county on this list — Williamson County, Texas — shows +533,137.
• Across the full universe of 612 county rows with both data points, the typical change was +70,899.
• The top gainers concentrate in Texas (9 of the top 25), California (6 of the top 25), Florida (4 of the top 25).

Where the pattern sits geographically

Texas (9 of the top 25), California (6 of the top 25), Florida (4 of the top 25) together account for the bulk of the top of this list. Click any county above to open its CensusEasy page, which carries the full historical time series for every metric we publish (income, education, housing, commute, race composition, industry mix), plus its rank within its state and its national percentile on each metric.

How to read this

This ranking is sorted by absolute change, not by percentage change. Absolute change is the figure that lines up with how readers experience these numbers in everyday life ("the typical household here earns $X more than in 1990"). The percentage-change framing surfaces a different set of county rows — usually places that started from a low base — and we publish those rankings separately on the rankings pages.

A single metric never tells the whole story. The smallest gain on this list can reflect either change in the same population staying in place, or compositional change as some residents leave and others arrive. Companion studies on poverty, education, and housing cost together describe the fuller picture.

Absolute gain favors already-large counties; the percentage growth ranking surfaces a different set of places (exurban counties that started small) and we publish that separately on the rankings pages.