According to the 2010 United States Census, the population of Petaluma was 57,941 people with a population density of 3,998.9 people per square mile. The population was divided into 21,737 households and 14,701 families.
Of the households, 34.7% had people under the age of 18 years old living in them, 24.7% were just individuals, and 10.9% had individuals 65 years old or older living alone. 52.4% of the households were opposite-sex married couples living together, 6.1% had unmarried opposite-sex couples living together, and 1% had same-sex couples either married or unmarried living together. 10.4% of the households had a single female head-of-house, whereas 4.8% had a single male head-of-house. The average household size was 2.63 and the average family size was 3.14.
In 2010, the age range in Petaluma broke down as follows: 23.2% of residents were under the age of 18, 7.9% were between 18 and 24 years of age, 26% of people were between 25 and 44, 29.8% were between 45 and 64, and 13.1% were 65 years old or older. The median age of Petaluma was 40.3 years old.
The racial makeup of Petaluma was as follows: 80.4% white residents, 16.2% Hispanic or Latino residents, 4.5% Asian residents, 1.4% black residents, .6% Native American residents, and .2% Pacific Islander residents. 8.8% of Petaluma residents identified as “other races,” and 4.1% identified as two or more races.