The welcome sign coming in the north side of the village.
|Area||2.14 sq mi (5.54 km2)|
|- land||2.12 sq mi (5 km2)|
|- water||0.02 sq mi (0 km2), 0.93%|
|Density||2,572.3 / sq mi (993.2 / km2)|
|Mayor||B. J. Hackler|
|- summer (DST)||CDT (UTC-5)|
St. Joseph is located at (40.112935, -88.037589).
According to the 2010 census, the village has a total area of 2.14 square miles (5.5 km2), of which 2.12 square miles (5.5 km2) (or 99.07%) is land and 0.02 square miles (0.052 km2) (or 0.93%) is water.
As of the census of 2004, there were 3,900 people, 2,014 households, and 1,002 families residing in the village. The population density was 3,024.3 people per square mile (995.0/km ). There were 1,157 housing units at an average density of 1,022.0 per square mile (395.3/km ). The racial makeup of the village was 98.90% White, 0.10% African American, 0.07% Native American, 0.24% Asian, 0.24% from other races, and 0.45% from two or more races. Hispanic or Latino of any race were 0.86% of the population.
There were 1,125 households out of which 40.1% had children under the age of 18 living with them, 65.4% were married couples living together, 6.9% had a female householder with no husband present, and 25.8% were non-families. 22.4% of all households were made up of individuals and 11.3% had someone living alone who was 65 years of age or older. The average household size was 2.58 and the average family size was 3.03.
In the village the population was spread out with 28.5% under the age of 18, 6.3% from 18 to 24, 33.0% from 25 to 44, 21.4% from 45 to 64, and 10.9% who were 65 years of age or older. The median age was 36 years. For every 100 females there were 94.5 males. For every 100 females age 18 and over, there were 92.3 males.
The median income for a household in the village was $53,424, and the median income for a family was $61,094. Males had a median income of $40,250 versus $29,450 for females. The per capita income for the village was $21,381. About 2.8% of families and 4.3% of the population were below the poverty line, including 4.0% of those under age 18 and 8.9% of those age 65 or over.