Diablo Grande is a census-designated place (CDP) in Stanislaus County, California. It is a gated bedroom community nestled in the Diablo Range, whence it gets its name. Diablo Grande sits at an elevation of 1,535 feet (468 m). It is about 9 miles (14 km) southwest of Patterson. The 2010 United States census reported Diablo Grande's population was 826.
A gated community and golf resort developed by Don Panoz, in May 1990, the Patterson city council received preliminary plans for Diablo Grande. The project was later approved in the fall of 1993. By 1999, the Stanislaus County superior court had rejected Diablo Grande's second environmental impact report with the argument that it had failed to properly protect the surrounding environment and there was no answer to where water would come from due to the area not containing adequate on-site water. In response to these claims, Diablo Grande created the Western Hills Water District to serve the community. Water transfers from former agriculture land to the community were arranged and 12,000 acres have been preserved for wildlife.
Developer Donald Panoz envisioned Diablo Grande to consist of 5,000 to 10,000 homes, a resort hotel and spa, six golf courses, an equestrian center, vineyards, a winery and commercial properties, including a high-tech research park. After investing $120 million into Diablo Grande and the financial crisis of 2007–08 occurring, the investors of the community filed for chapter 11 bankruptcy on March 10, 2008. There were more than $54 million in unpaid debts and 70 out of the 350 homes built faced foreclosure.
In October 2008, World International LLC purchased Diablo Grande for $20 million. The California Department of Health temporarily suspended new building permits in January 2009 when water tests showed Trihalomethane levels at 0.103 milligrams per liter vs. the state standard of 0.080 milligrams per liter.
Diablo Grande's Legends golf course, designed by Jack Nicklaus and Gene Sarazen, was closed in March 2014 due to the drought in California.
According to the United States Census Bureau, the CDP covers an area of 5.1 square miles (13.2 km²), 99.99% of it land and 0.01% of it water.
The 2010 United States Census reported that Diablo Grande had a population of 826. The population density was 161.5 people per square mile (62.4/km²). The racial makeup of Diablo Grande was 510 (61.7%) White, 77 (9.3%) African American, 3 (0.4%) Native American, 70 (8.5%) Asian, 6 (0.7%) Pacific Islander, 77 (9.3%) from other races, and 83 (10.0%) from two or more races. Hispanic or Latino of any race were 254 persons (30.8%).
The census reported that 826 people (100% of the population) lived in households, 0 (0%) lived in non-institutionalized group quarters, and 0 (0%) were institutionalized.
There were 307 households, out of which 107 (34.9%) had children under the age of 18 living in them, 192 (62.5%) were opposite-sex married couples living together, 25 (8.1%) had a female householder with no husband present, 14 (4.6%) had a male householder with no wife present. There were 18 (5.9%) unmarried opposite-sex partnerships, and 6 (2.0%) same-sex married couples or partnerships. 54 households (17.6%) were made up of individuals and 5 (1.6%) had someone living alone who was 65 years of age or older. The average household size was 2.69. There were 231 families (75.2% of all households); the average family size was 3.09.
The population was spread out with 217 people (26.3%) under the age of 18, 47 people (5.7%) aged 18 to 24, 249 people (30.1%) aged 25 to 44, 249 people (30.1%) aged 45 to 64, and 64 people (7.7%) who were 65 years of age or older. The median age was 37.9 years. For every 100 females there were 110.7 males. For every 100 females age 18 and over, there were 107.1 males.
There were 422 housing units at an average density of 82.5 per square mile (31.9/km²), of which 241 (78.5%) were owner-occupied, and 66 (21.5%) were occupied by renters. The homeowner vacancy rate was 10.6%; the rental vacancy rate was 16.0%. 615 people (74.5% of the population) lived in owner-occupied housing units and 211 people (25.5%) lived in rental housing units.