Colusa is on the Sacramento River, which has a high levee so that the river is not clearly apparant from the city.
Colusa features an old historic Chinatown, and also a beautiful Carnegie Library building constrcted in 1905. There is an architecturally noteworthy courthouse built in a classical style. The city was founded by persons from Mississippi, and with its quaint cottages and lush gardens it gives the appearance of a small Southern town.
Charles D. Semple purchased the land on which Colusa was founded in 1849 and called the place Salmon Bend. The town was founded, under the name Colusi, by Semple in 1850. The first post office was established the following year, 1851. The California legislature changed the town's (and the county's) name to Colusa in 1854. The town flourished due to its location on the Southern Pacific Railroad. Several travelers rest stops were established at various road distances from Colusa, including Five Mile House, Seven Mile House, Nine Mile House, Ten Mile House, Eleven Mile House, Fourteen Mile House (also called Sterling Ranch), Sixteen Mile House (at the current location of Princeton), and Seventeen Mile House. The original settlement of what became Colusa was originally placed at the site of Seven Mile House but subsequently removed to its current site in 1850.
As of the census of 2000, there were 5,402 people, 1,897 households, and 1,365 families residing in the city. The population density was 3,244.0 people per square mile (1,248.9/km²). There were 2,016 housing units at an average density of 1,210.7/sq mi (466.1/km²). The racial makeup of the city was 68.66% White, 0.30% Black or African American, 1.76% Native American, 1.46% Asian, 0.78% Pacific Islander, 23.29% from other races, and 3.76% from two or more races. 41.71% of the population were Hispanic or Latino of any race.
There were 1,897 households out of which 40.6% had children under the age of 18 living with them, 54.7% were married couples living together, 11.8% had a female householder with no husband present, and 28.0% were non-families. 23.7% of all households were made up of individuals and 10.8% had someone living alone who was 65 years of age or older. The average household size was 2.81 and the average family size was 3.33.
In the city the population was spread out with 30.2% under the age of 18, 10.2% from 18 to 24, 28.2% from 25 to 44, 20.0% from 45 to 64, and 11.4% who were 65 years of age or older. The median age was 32 years. For every 100 females there were 99.7 males. For every 100 females age 18 and over, there were 98.9 males.
The median income for a household in the city was $35,250, and the median income for a family was $41,833. Males had a median income of $32,006 versus $20,510 for females. The per capita income for the city was $15,251. About 14.2% of families and 17.2% of the population were below the poverty line, including 20.0% of those under age 18 and 8.9% of those age 65 or over. Also the death place of 20th Century baseball star Hal Chase of the New York highlanders and Giants
In the state legislature Colusa is located in the 4th Senate District, represented by Republican Sam Aanestad, and in the 2nd Assembly District, represented by Republican Jim Nielsen. Federally, Colusa is located in California's 2nd congressional district, which has a Cook PVI of R +13 and is represented by Republican Wally Herger.