Other notable streets in Union include Martindale Road, Sweet Potato Ridge Road, and Phillipsburg-Union Road.
On November 18, 2006 Mayor Robert Packard died after collapsing while performing a wedding at city hall. Due to the city's charter the Vice-mayor (Larry Beyer) became the new mayor of Union.
As of the census of 2000, there were 5,574 people, 2,080 households, and 1,609 families residing in the city. The population density was 1,302.0 people per square mile (502.8/km²). There were 2,167 housing units at an average density of 506.2/sq mi (195.5/km²). The racial makeup of the city was 96.88% White, 0.91% African American, 0.14% Native American, 0.36% Asian, 0.02% Pacific Islander, 0.36% from other races, and 1.33% from two or more races. Hispanic or Latino of any race were 1.18% of the population.
There were 2,080 households out of which 40.1% had children under the age of 18 living with them, 61.1% were married couples living together, 11.8% had a female householder with no husband present, and 22.6% were non-families. 18.9% of all households were made up of individuals and 5.6% had someone living alone who was 65 years of age or older. The average household size was 2.68 and the average family size was 3.05.
In the city the population was spread out with 28.7% under the age of 18, 7.6% from 18 to 24, 33.2% from 25 to 44, 22.6% from 45 to 64, and 7.9% who were 65 years of age or older. The median age was 34 years. For every 100 females there were 92.9 males. For every 100 females age 18 and over, there were 91.6 males.
The median income for a household in the city was $50,471, and the median income for a family was $55,139. Males had a median income of $39,944 versus $25,430 for females. The per capita income for the city was $21,260. About 2.5% of families and 3.7% of the population were below the poverty line, including 3.5% of those under age 18 and 3.5% of those age 65 or over.
East of the Stillwater River, students attend Vandalia-Butler City School District.