Hilmar-Irwin is located at 37°24′30″N 120°51′3″W, west of Delhi and Livingston and south of Turlock.
According to the United States Census Bureau, the CDP has a total area of 3.9 square miles (10 km2), all of it land.
It is home to the Hilmar Cheese Company, a cheese manufacturer that offers public tours.
The 2010 United States Census reported that Hilmar-Irwin had a population of 5,197. The population density was 1,323.1 people per square mile (510.9/km²). The racial makeup of Hilmar-Irwin was 4,475 (86.1%) White, 15 (0.3%) African American, 23 (0.4%) Native American, 87 (1.7%) Asian, 1 (0.0%) Pacific Islander, 439 (8.4%) from other races, and 157 (3.0%) from two or more races. Hispanic or Latino of any race were 916 persons (17.6%).
The Census reported that 5,197 people (100% of the population) lived in households, 0 (0%) lived in non-institutionalized group quarters, and 0 (0%) were institutionalized.
There were 1,755 households, out of which 694 (39.5%) had children under the age of 18 living in them, 1,082 (61.7%) were opposite-sex married couples living together, 205 (11.7%) had a female householder with no husband present, 106 (6.0%) had a male householder with no wife present. There were 82 (4.7%) unmarried opposite-sex partnerships, and 15 (0.9%) same-sex married couples or partnerships. 301 households (17.2%) were made up of individuals and 158 (9.0%) had someone living alone who was 65 years of age or older. The average household size was 2.96. There were 1,393 families (79.4% of all households); the average family size was 3.32.
The population was spread out with 1,390 people (26.7%) under the age of 18, 483 people (9.3%) aged 18 to 24, 1,289 people (24.8%) aged 25 to 44, 1,323 people (25.5%) aged 45 to 64, and 712 people (13.7%) who were 65 years of age or older. The median age was 36.2 years. For every 100 females there were 96.9 males. For every 100 females age 18 and over, there were 91.8 males.
There were 1,841 housing units at an average density of 468.7 per square mile (181.0/km²), of which 1,288 (73.4%) were owner-occupied, and 467 (26.6%) were occupied by renters. The homeowner vacancy rate was 0.9%; the rental vacancy rate was 6.8%. 3,672 people (70.7% of the population) lived in owner-occupied housing units and 1,525 people (29.3%) lived in rental housing units.
As of the census of 2000, there were 4,807 people, 1,602 households, and 1,315 families residing in the CDP. The population density was 1,226.8 people per square mile (473.5/km²). There were 1,646 housing units at an average density of 420.1 per square mile (162.1/km²). The racial makeup of the CDP was 77.93% White, 0.35% Black or African American, 0.33% Native American, 2.39% Asian, 6.59% from other races, and 12.40% from two or more races. Hispanic or Latino of any race were 12.38% of the population.
There were 1,602 households out of which 42.0% had children under the age of 18 living with them, 67.9% were married couples living together, 9.5% had a female householder with no husband present, and 17.9% were non-families. 14.6% of all households were made up of individuals and 8.9% had someone living alone who was 65 years of age or older. The average household size was 3.00 and the average family size was 3.32.
In the CDP, the population was spread out with 29.0% under the age of 18, 9.0% from 18 to 24, 29.5% from 25 to 44, 19.3% from 45 to 64, and 13.2% who were 65 years of age or older. The median age was 34 years. For every 100 females there were 98.1 males. For every 100 women age 18 and over, there are 93.7 men.
The median income for a household in the CDP was $40,951, and the median income for a family was $46,250. Males had a median income of $35,244 versus $23,551 for females. The per capita income for the CDP was $16,113. About 4.3% of families and 6.4% of the population were below the poverty line, including 7.3% of those under age 18 and 4.1% of those age 65 or over.
In the state legislature, Hilmar-Irwin is located in the 12th Senate District, represented by Republican Anthony Cannella, and in the 21st Assembly District, represented by Democrat Adam Gray.
In the United States House of Representatives, Hilmar-Irwin is in California's 16th congressional district, represented by Democrat Jim Costa.
2012 Citizen Redstricting:
Hilmar will now belong to CA State Assembly District 21. CA State Assembly District 17 is now a Bay Area assembly district.