Located in Petaluma is the Rancho Petaluma Adobe, a National Historic Landmark. It was built beginning in 1836 by General Mariano Guadalupe Vallejo, then Commandant of the San Francisco Presidio. It was the center of a vast 66,000 acre (270-km²) ranch stretching from Petaluma Creek to Sonoma Creek. The adobe is considered one of the best preserved buildings of its era in Northern California.
Petaluma is a transliteration of the Coast Miwok phrase péta lúuma which means hill backside and probably refers to Petaluma's proximity to Sonoma Mountain.
Petaluma has a well preserved, historic city center which includes many buildings that survived the great 1906 earthquake.
As of the census of 2000, there were 54,548 people, 19,932 households, and 14,012 families residing in the city. The population density was 3,953 people per square mile (1,526/km²). There were 20,304 housing units at an average density of 1,471/sq mi (568/km²). The racial makeup of the city was 84.16% White, 1.16% African American, 0.54% Native American, 3.91% Asian, 0.17% Pacific Islander, 6.08% from other races, and 3.98% from two or more races. 14.64% of the population were Hispanic.
There were 19,932 households out of which 36.6% had children under the age of 18 living with them, 55.3% were married couples living together, 10.6% had a female householder with no husband present, and 29.7% were non-families. 22.6% of all households were made up of individuals and 9.1% had someone living alone who was 65 years of age or older. The average household size was 2.70 and the average family size was 3.16. The age distribution is: 26.2% under the age of 18, 7.2% from 18 to 24, 31.5% from 25 to 44, 24.1% from 45 to 64, and 11.0% who were 65 years of age or older. The median age was 37 years. For every 100 females there were 95.6 males. For every 100 females age 18 and over, there were 91.9 males.
The median income for a household in the city was $61,679, and the median income for a family was $71,158 (these figures had risen to $68,949 and $85,513 respectively as of a 2007 estimate). Males had a median income of $50,232 versus $36,413 for females. The per capita income for the city was $27,087. About 3.3% of families and 6.0% of the population were below the poverty line, including 6.2% of those under age 18 and 7.1% of those age 65 or over.
Highway 101 is the main freeway through town. State Route 116 also runs through town as Lakeville Highway. Other major streets include East Washington Street, North and South McDowell Boulevards, and Petaluma Boulevard.
Petaluma is served by Petaluma Transit, Golden Gate Transit and by Sonoma County Transit bus services.
The nearest major airports are San Francisco and Oakland International Airport. General aviation is served by the Petaluma Municipal Airport.