San Mateo County vs Santa Clara County
Two neighbouring counties in California, compared on population, size, income and housing. They share 24 mi of border.
San Mateo County
California
Santa Clara County
California
Both outlines are drawn at true relative size. Santa Clara County spans about 76.8 km at its widest.
Side by side
| Measure | San Mateo County | Difference | Santa Clara County |
|---|---|---|---|
| Population | 743,568 | -61.2% | 1,914,391 |
| Change since 2020 | -2.5% | -1.6 pp | -0.9% |
| Land area | 448.6 sq mi | -65.3% | 1,291 sq mi |
| Population density | 1,658 per sq mi | +11.8% | 1,483 per sq mi |
| Median household income | $158,855 | -3.3% | $164,281 |
| Median home value | $1,559,600 | +4.6% | $1,490,600 |
| Median age | 40.9 | +7.3% | 38.1 |
| Households | 264,419 | -59.9% | 659,353 |
| Housing units | 287,184 | -58.9% | 698,837 |
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; US Census Bureau, American Community Survey, American Community Survey 2020-2024 5-Year Estimates, released 29 January 2026; US Census Bureau, County Adjacency File, 2025 County Adjacency File, released 15 September 2025. The difference column is computed here: the first county's figure against the second, expressed as a percentage of the second. The change-since-2020 row is the exception: two growth rates differ in percentage points (pp), not percent. Retrieved 30 August 2026.
What the numbers say
- Santa Clara County holds about 2.6 times the population of San Mateo County: 1,914,391 against 743,568.
- Santa Clara County covers more ground, at 1,291 square miles against 448.6.
- San Mateo County is the more crowded of the two, at 1,658 people per square mile against 1,483.
- Median household income is higher in Santa Clara County, by 5,426 dollars a year.
- Since 2020, San Mateo County has shrunk by 2.5% and Santa Clara County has shrunk by 0.9%.
- They share 24 mi of common border, which the Census Bureau publishes in its county adjacency file and which almost no other county reference presents.
Full pages
Want a different pair? Compare any two of the 3,144 US counties.
Rebuilt from source data 30 August 2026. How these figures are produced.