San Geronimo, California Demographics & Population 2026

A note before these figures: with a population of 583, San Geronimo's ACS estimates come from a small number of survey responses and carry wide margins of error. Individual percentages below — particularly rates that round to 0% or 100% — are approximations, not precise measurements. See data.census.gov for the published margins of error.

Population Overview

San Geronimo is a small community located in California, within Marin County. The total population is 583. It ranks as the 1182nd most populous out of 1,570 Census-designated places in California.

Age Demographics

The median age in San Geronimo is 46.5 years. This is 23% higher than the state median of 37.9 years. 15.8% of residents are 75 or older, suggesting a significant retirement-age population with implications for healthcare services and senior housing.

Economy, Income & Housing

The median household income in San Geronimo is $171,932. This is 73% higher than the state median of $99,122. It is also 113% higher than the national median of $80,734. The ACS records no residents below the poverty line in San Geronimo. In a community this small the estimate rests on very few survey responses, so it should be read as an absence of measurement rather than a measured absence of poverty. The survey records no unemployed residents in San Geronimo, which reflects the size of the sample rather than a labor market without joblessness. The median home value is $1,175,500. Housing costs are 60% higher than the state median of $734,700. The home-value-to-income ratio of 6.8x suggests that housing affordability is a significant concern for many residents. 90.3% of occupied housing units are owner-occupied. This homeownership rate is 62% higher than the state average of 55.9%.

Race & Ethnicity

San Geronimo has a predominantly White (non-Hispanic) population, comprising 86.5% of all residents. Hispanic or Latino residents account for 3.4%. The White (non-Hispanic) population is significantly higher than the state average (86.5% vs 33.8%). The Black or African American population (0.2%) is well below the state average of 5.2%. The Hispanic or Latino population (3.4%) is well below the state average of 40.2%.

Education

94.5% of residents aged 25 and older hold a bachelor's degree or higher. This places San Geronimo in the top 10% of all cities in the state for educational attainment. This is 155% higher than the state rate of 37.1%. Nationally, 35.7% of adults hold at least a bachelor's degree. No surveyed resident aged 25 or older reported leaving school before earning a high school diploma, though a rate of exactly 100% reflects the limits of a small sample. Notably, 75.6% of adults hold a graduate or professional degree, indicating a highly educated workforce.

Data Sources & Methodology

All demographic data for San Geronimo, California is sourced from the U.S. Census Bureau's American Community Survey (ACS) 2020–2024 5-Year Estimates. The ACS collects data from approximately 3.5 million households annually and pools five years of responses so that even small communities can be measured, though the margin of error widens as the population falls. Comparisons are made against California state averages and national averages calculated from the same dataset. Rankings reflect the city's position among all 1,570 Census-designated places in California. Read more about how these figures are produced on our methodology page, or visit data.census.gov for official data.