Throughout the first half of the 20th century Waterbury had large industrial interests, and was the leading center of the United States for the manufacture of brassware (including castings and finishings), as reflected in the nickname the "Brass City" and the city's motto Quid Aere Perennius, Latin for "What Is More Lasting Than Brass[?]". It was noted for the manufacture of watches and clocks.
As of the census of 2000, there were 107,271 people, 42,622 households, and 26,894 families residing in the city. The population density was 3,754.7 people per square mile (1,449.7/km²). There were 46,827 housing units at an average density of 1,639.0/sq mi (632.8/km²). The racial makeup of the city was 67.14% White, 16.31% Black or African American, 0.42% Native American, 1.51% Asian, 0.06% Pacific Islander, 10.91% from other races, and 3.66% from two or more races. Hispanic or Latino of any race were 21.77% of the population.
Waterbury is probably the most heavily Italian-American large city in Connecticut today. The Italian influence is especially strong in the Town Plot, Brooklyn, and North End neighborhoods. It has been said that 6 in 10 voters in Waterbury is of Italian descent and they often prove to be a decisive voting block in city elections. Additionally, the city is home to thriving French-Canadian, Portuguese, Lebanese, Lithuanian, and Albanian communities. Waterbury has strong Irish roots as well, especially in Washington Hill which is home to the city's annual St. Patrick Day's Parade. At the beginning of the 21st century, Waterbury had a growing Orthodox Jewish population.
There were 42,622 households out of which 31.2% had children under the age of 18 living with them, 38.8% were married couples living together, 19.1% had a female householder with no husband present, and 36.9% were non-families. 31.4% of all households were made up of individuals and 12.1% had someone living alone who was 65 years of age or older. The average household size was 2.46 and the average family size was 3.11.
In the city the population was spread out with 26.5% under the age of 18, 8.9% from 18 to 24, 29.9% from 25 to 44, 19.7% from 45 to 64, and 15.0% who were 65 years of age or older. The median age was 35 years. For every 100 females there were 89.9 males. For every 100 females age 18 and over, there were 85.8 males.
The median income for a household in the city was $34,285, and the median income for a family was $42,300. Males had a median income of $35,486 versus $27,428 for females. The per capita income for the city was $17,701. About 12.7% of families and 16.0% of the population were below the poverty line, including 23.6% of those under age 18 and 11.1% of those age 65 or over.