In general, San Marino is a small, well educated community largely populated by professionals and their families. The city is primarily known for its immaculately preserved housing stock, its strict zoning laws, and its schools.
The city is divided into seven zones, based on minimum lot size. The smallest lot size is about 4500 square feet, with many averaging over 30,000 square feet. Because of this and other factors, most of the homes in San Marino, built between 1920 and 1950, do not resemble the houses in surrounding Southern California neighborhoods (with the exception perhaps of neighboring Pasadena). San Marino has also fostered a sense of historic preservation among its homeowners. The city's strict zoning laws have thus far prevented the development of "McMansions," found elsewhere in Los Angeles. Generally speaking, San Marino homes are older, bigger and more genteel than those in other communities. No apartment buildings exist in the city.
To Southern Californians, San Marino was once known as one of the oldest of old-money wealth and a bastion of Southern California's WASP gentility. Yet, today Asians constitute the plurality of the population with nearly 40% of the population being foreign born. Recently, San Marino has seen an influx of Asians, mostly Chinese Americans. San Marino may in fact be more recognizable to most Americans than those other Southern California communities, due to the prevalence of filming in the city. Many television shows, such as The Fresh Prince of Bel Air and CSI: Crime Scene Investigation have actually been filmed in San Marino and Pasadena. Location scouts also turn to San Marino when they wish to film a series in Southern California that takes place elsewhere. The atypical housing stock in the city, including Georgian and faux antebellum mansions cause certain neighborhoods resemble the East Coast.
San Marino is also regarded as having one of the best-performing schools in the Greater Los Angeles area. Its high school consistently ranks as the one of the highest API score among public high schools in California. All of its public schools are distinguished as California "Blue Ribbon" schools.
The city includes the estate of Henry E. Huntington, who made a fortune in the development of Southern California and opened the library and art collections in his large neo-Palladian mansion to the public in 1919, best known as the Huntington Library. At the time, San Marino was some twelve miles from Los Angeles. Huntington Drive and Sierra Madre Boulevard serve as the main thoroughfares, leading to Pasadena, Alhambra and San Gabriel.
Another landmark is the Michael White Adobe House, located on the high school campus.
In the middle of San Marino lies Lacy Park, a huge expanse of grass and trees rare for urban areas. Lacy Park was created when Wilson Lake was drained, and was modeled after New York's Central Park.
The Old Mill, completed about 1816 as a grist mill for Mission San Gabriel, is in San Marino. The original two-story structure measured 53 by 26 feet. It is the oldest commercial building in Southern California.
As of the censusGR2 of 2000, there were 12,945 people, 4,266 households, and 3,673 families residing in the city. The population density was 3,430.5/mi² (1,325.8/km²). There were 4,437 housing units at an average density of 1,175.8/mi² (454.4/km²). The racial makeup of the city was 47.7% White, 0.25% African American, 0.05% Native American, 48.6% Asian, 0.08% Pacific Islander, 1.04% from other races, and 2.30% from two or more races. Hispanic or Latino of any race were 6.25% of the population. More than a third of the city's populatio, 37.6% were born outside the United States.
There were 4,266 households out of which 42.0% had children under the age of 18 living with them, 75.0% were married couples living together, 8.6% had a female householder with no husband present, and 13.9% were non-families. 12.0% of all households were made up of individuals and 7.3% had someone living alone who was 65 years of age or older. The average household size was 3.03 and the average family size was 3.29.
In the city the population is spread out with 26.5% under the age of 18, 6.4% from 18 to 24, 21.5% from 25 to 44, 29.4% from 45 to 64, and 16.2% who are 65 years of age or older. The median age is 43 years. For every 100 females there were 93.1 males. For every 100 females age 18 and over, there were 89.1 males.
The median income for a household in the city was $117,267, and the median income for a family was $125,708. Males had a median income of $98,928 versus $51,853 for females. The per capita income for the city was $59,150. About 3.7% of families and 5.0% of the population were below the poverty line, including 4.8% of those under age 18 and 3.0% of those age 65 or over. The vast majority, 69.7% of persons had a Bachelor's degree or higher, compared to 27.2% at the national average, respectively.
There are four public schools in San Marino: Valentine Elementary School, Carver Elementary School, Huntington Middle School, and San Marino High School. Southwestern Academy, a private college preparatory school, is also located in San Marino.
In 2005 and 2006, the San Marino Unified School District ranked first among all 328 California unified school districts based on the California Academic Performance Index. San Marino High School is considered one of the best-performing public schools on Standardized Achievement Tests (as of 2004) in Southern California. It was also named a National Blue Ribbon School in 2006. Most of San Marino's schools' funds come from private donors and organizations. 
Asian Americans are 70% of San Marino school enrollment as of December 2005.
As San Marino is wary of admitting chain businesses, there are few restaurants in town, all of which rest on Huntington Drive or Mission Street. Big-box stores are practically non-existent in the area.
Julienne (on Mission) is one of the best known restaurants in the area. It is an upscale bistro with popular patio dining.
Tony's Pizza, a local favorite that delivers only within San Marino, is located next to the high school.
Colonial Kitchen is a quaint place to go for traditional American food.
Yoshida is a great Japanese restaurant and sushi bar on Huntington Drive.
Vanille is a new store that opened in 2003 sells European-style pastries with a distinct Asian tone.
There is one Starbucks in San Marino, on the corner of Sierra Madre Blvd. and Huntington Drive (the Starbucks just east of San Gabriel Blvd. is in unincorporated county territory).
Tong Dang is a Thai restaurant on Huntington Drive, just east of Oak Knoll.
In 2007, Ice Cream Shop, selling Fosselman's Ice Cream, opened next to the hardware store on Huntington Drive.
Right across the street outside the city limit for San Marino is a large area which contains a Hows Supermarket, Subway, Starbucks, B-Man's Burgers, and Baskin Robbins. San Marino Academy, a tutoring center, is also there.
San Marino also is home to the San Marino Grill which has been under the same ownership for over forty years.