|Elevation||397 ft (121 m)|
|- summer (DST)||CDT (UTC-5)|
The Modoc Rock Shelter, a U.S. National Historic Landmark, is located near Modoc and the Ste. Genevieve-Modoc Ferry across the Mississippi River connects Modoc and the surrounding communities with Ste. Genevieve, Missouri.
The area's population was 221 at the 2000 census.
Modoc is located at(38.0525522 -90.0373334).
There were 96 households out of which 29.2% had children under the age of 18 living with them, 55.2% were married couples living together, 6.3% had a female householder with no husband present, and 36.5% were non-families. 34.4% of all households were made up of individuals living alone and 11.5% had someone living alone who was 65 years of age or older. The average household size was 2.30 and the average family size was 2.97.
In the ZCTA the population was spread out with 25.7% under the age of 18, 61.9% from 19 to 64, and 12.4% who were 65 years of age or older. The median age was 41.3 years. The population is 49.8% male and 50.2% female.