There were 3,592 households out of which 32.5% had children under the age of 18 living with them, 42.5% were married couples living together, 18.3% had a female householder with no husband present, and 35.5% were non-families. 29.3% of all households were made up of individuals and 11.2% had someone living alone who was 65 years of age or older. The average household size was 2.37 and the average family size was 2.94.
In the city the population was spread out with 25.8% under the age of 18, 16.1% from 18 to 24, 25.9% from 25 to 44, 18.7% from 45 to 64, and 13.4% who were 65 years of age or older. The median age was 31 years. For every 100 females there were 87.2 males. For every 100 females age 18 and over, there were 83.5 males.
The median income for a household in the city was $26,821, and the median income for a family was $36,615. Males had a median income of $32,029 versus $21,546 for females. The per capita income for the city was $16,113. About 14.8% of families and 20.1% of the population were below the poverty line, including 24.5% of those under age 18 and 20.2% of those age 65 or over.
Monticello is home to two school districts, Monticello Public Schools and Drew Central, the latter of which primarily serves outlying areas. High School football is a popular community event; the Monticello Billies won the AAA (now AAAA) state championship in 1994 and the Jr. Billies (from Monticello Junior High) were undefeated in the years from 2005-2008. The Pirates, the Drew Central football team, were recently reincorporated after a fire destroyed the team's equipment.