Trimble was named after J. M. Trimble, a railroad official. The city was originally called Carpenter's Store; the town site was platted and present name adopted when the railroad was extended to that point. A post office called Carpenters Store was established in 1858, and the name was changed to Trimble in 1899.
As of the census of 2010, there were 646 people, 269 households, and 177 families residing in the city. The population density was. There were 283 housing units at an average density of. The racial makeup of the city was 97.7% White, 0.6% African American, 0.3% from other races, and 1.4% from two or more races. Hispanic or Latino of any race were 0.9% of the population. There were 269 households of which 32.0% had children under the age of 18 living with them, 46.1% were married couplesliving together, 10.8% had a female householder with no husband present, 8.9% had a male householder with no wife present, and 34.2% were non-families. 28.6% of all households were made up of individuals and 6.7% had someone living alone who was 65 years of age or older. The average household size was 2.40 and the average family size was 2.93. The median age in the city was 37.3 years. 24.5% of residents were under the age of 18; 9.6% were between the ages of 18 and 24; 25.3% were from 25 to 44; 28.7% were from 45 to 64; and 11.9% were 65 years of age or older. The gender makeup of the city was 51.1% male and 48.9% female.
2000 census
As of the census of 2000, there were 451 people, 188 households, and 116 families residing in the city. The population density was 923.0 people per square mile. There were 199 housing units at an average density of 407.3 per square mile. The racial makeup of the city was 97.56% White, 0.44% African American, 0.89% Asian, and 1.11% from two or more races. Hispanic or Latino of any race were 0.22% of the population. There were 188 households out of which 33.0% had children under the age of 18 living with them, 51.1% were married couples living together, 6.4% had a female householder with no husband present, and 37.8% were non-families. 34.6% of all households were made up of individuals and 18.1% had someone living alone who was 65 years of age or older. The average household size was 2.40 and the average family size was 3.13. In the city the population was spread out with 28.6% under the age of 18, 6.2% from 18 to 24, 29.7% from 25 to 44, 23.7% from 45 to 64, and 11.8% who were 65 years of age or older. The median age was 37 years. For every 100 females, there were 101.3 males. For every 100 females age 18 and over, there were 97.5 males. The median income for a household in the city was $38,571, and the median income for a family was $47,813. Males had a median income of $37,639 versus $21,645 for females. The per capita income for the city was $17,715. About 7.1% of families and 10.7% of the population were below the poverty line, including 9.8% of those under age 18 and 26.7% of those age 65 or over.
