San Geronimo (Spanish: San Gerónimo, meaning "St. Jerome") is a census-designated place (CDP) located in the San Geronimo Valley in Marin County, California, United States. San Geronimo is bordered by Lagunitas-Forest Knolls to its west and Woodacre to its east. It is southwest of downtown Novato at an elevation of . Prior to 1877, the place was called Nicasio. In 2018, The Trust for Public Land purchased the site and has opened it to public access as a park while it works to restore habitat and conduct a planning process for future use.
Demographics
San Geronimo first appeared as a census designated place in the 2000 U.S. census formed out of part of the Lagunitas-Forest Knolls CDP and the Woodacre CDP.
!Pop 2010
!style="background-color: #ffffb3;" |Pop 2020
!% 2000
!% 2010
!style="background-color: #ffffb3;" |% 2020
|-
|White alone (NH)
|398
|404
|style='background: #ffffe6; |416
|91.28%
|90.58%
|style='background: #ffffe6; |81.57%
|-
|Black or African American alone (NH)
|4
|3
|style='background: #ffffe6; |8
|0.92%
|0.67%
|style='background: #ffffe6; |1.57%
|-
|Native American or Alaska Native alone (NH)
|3
|2
|style='background: #ffffe6; |2
|0.69%
|0.45%
|style='background: #ffffe6; |0.39%
|-
|Asian alone (NH)
|4
|3
|style='background: #ffffe6; |6
|0.92%
|0.67%
|style='background: #ffffe6; |1.18%
|-
|Native Hawaiian or Pacific Islander alone (NH)
|2
|0
|style='background: #ffffe6; |5
|0.46%
|0.00%
|style='background: #ffffe6; |0.98%
|-
|Other race alone (NH)
|1
|2
|style='background: #ffffe6; |5
|0.23%
|0.45%
|style='background: #ffffe6; |0.98%
|-
|Mixed race or Multiracial (NH)
|13
|11
|style='background: #ffffe6; |30
|2.98%
|2.47%
|style='background: #ffffe6; |5.88%
|-
|Hispanic or Latino (any race)
|11
|21
|style='background: #ffffe6; |38
|2.52%
|4.71%
|style='background: #ffffe6; |7.45%
|-
|Total
|436
|446
|style='background: #ffffe6; |510
|100.00%
|100.00%
|style='background: #ffffe6; |100.00%
|}
2020
The 2020 United States census reported that San Geronimo had a population of 510. The population density was . The racial makeup of San Geronimo was 426 (83.5%) White, 8 (1.6%) African American, 8 (1.6%) Native American, 6 (1.2%) Asian, 5 (1.0%) Pacific Islander, 9 (1.8%) from other races, and 48 (9.4%) from two or more races. Hispanic or Latino of any race were 38 persons (7.5%).
The census reported that 505 people (99.0% of the population) lived in households and 5 (1.0%) were institutionalized.
The age distribution was 105 people (20.6%) under the age of 18, 12 people (2.4%) aged 18 to 24, 70 people (13.7%) aged 25 to 44, 163 people (32.0%) aged 45 to 64, and 160 people (31.4%) who were 65years of age or older. The median age was 54.3years. For every 100 females, there were 93.9 males.
The census reported that 100% of the population lived in households.
There were 199 households, 49 (24.6%) had children under the age of 18 living in them, 108 (54.3%) were opposite-sex married couples living together, 19 (9.5%) had a female householder with no husband present, 7 (3.5%) had a male householder with no wife present. There were 13 (6.5%) unmarried opposite-sex partnerships, and 2 (1.0%) same-sex married couples or partnerships. 43 households (21.6%) were one person and 9 (4.5%) had someone living alone who was 65 or older. The average household size was 2.24. There were 134 families (67.3% of households); the average family size was 2.60.
The age distribution was 72 people (16.1%) under the age of 18, 20 people (4.5%) aged 18 to 24, 89 people (20.0%) aged 25 to 44, 189 people (42.4%) aged 45 to 64, and 76 people (17.0%) who were 65 or older. The median age was 50.0 years. For every 100 females there were 97.3 males. For every 100 females age 18 and over, there were 94.8 males.
There were 208 housing units at an average density of , of which 73.4% were owner-occupied and 26.6% were occupied by renters. The homeowner vacancy rate was 0%; the rental vacancy rate was 0%. 76.5% of the population lived in owner-occupied housing units and 23.5% lived in rental housing units.
2000
At the 2000 census, the median household income was $58,542 and the median family income was $60,875. Males had a median income of $70,536 versus $32,292 for females. The per capita income for the CDP was $31,960. About 9.9% of families and 10.4% of the population were below the poverty line, including 18.4% of those under age 18 and none of those age 65 or over.
Education
San Geronimo is served by the Lagunitas Elementary School District and the Tamalpais Union High School District.