Grimes is located near the Sacramento River, on Highway 45 between Colusa and Knight's Landing. There is a convenience store, a small post office, a public library, and an elementary school. The school features grades Kindergarten through 5th grade, however some years the school will take 6th graders due to its small student count. There is a boat landing on the river to the south of the town, which also serves as a restaurant for the community.
The 2020 U.S. Census reported that Grimes had a population of 296. The population density was 172.9 inhabitants per square mile (66.8/km2). The racial makeup of Grimes was 284 (72.6%) White, 7 (1.8%) African American, 3 (0.8%) Native American, 1 (0.3%) Asian, 0 (0.0%) Pacific Islander, 65 (16.6%) from other races, and 31 (7.9%) from two or more races. Hispanic or Latino of any race were 196 persons (66.0%).
The Census reported that 391 people (100% of the population) lived in households, 0 (0%) lived in non-institutionalized group quarters, and 0 (0%) were institutionalized.
There were 130 households, out of which 48 (36.9%) had children under the age of 18 living in them, 73 (56.2%) were opposite-sex married couples living together, 13 (10.0%) had a female householder with no husband present, 5 (3.8%) had a male householder with no wife present. There were 10 (7.7%) unmarried opposite-sex partnerships, and 0 (0%) same-sex married couples or partnerships. 33 households (25.4%) were made up of individuals, and 12 (9.2%) had someone living alone who was 65 years of age or older. The average household size was 3.01. There were 91 families (70.0% of all households); the average family size was 3.70.
The population was spread out, with 120 people (30.7%) under the age of 18, 31 people (7.9%) aged 18 to 24, 96 people (24.6%) aged 25 to 44, 104 people (26.6%) aged 45 to 64, and 40 people (10.2%) who were 65 years of age or older. The median age was 33.6 years. For every 100 females, there were 96.5 males. For every 100 females age 18 and over, there were 97.8 males.
There were 145 housing units at an average density of 64.1 units per square mile (24.7 units/km2), of which 130 were occupied, of which 71 (54.6%) were owner-occupied, and 59 (45.4%) were occupied by renters. The homeowner vacancy rate was 4.1%; the rental vacancy rate was 9.2%. 210 people (53.7% of the population) lived in owner-occupied housing units and 181 people (46.3%) lived in rental housing units.
^ abcdeDurham, David L. (1998). California's Geographic Names: A Gazetteer of Historic and Modern Names of the State. Clovis, Calif.: Word Dancer Press. p. 495. ISBN1-884995-14-4.