| Official Name: | Saint Mary's Township |
| Settlement Type: | Township |
| Image Map1: | Map of Illinois highlighting Hancock County.svg |
| Mapsize1: | 150px |
| Map Caption1: | Hancock County's location in Illinois |
| Subdivision Type: | Country |
| Subdivision Type1: | State |
| Subdivision Type2: | County |
| Subdivision Name2: | Hancock |
| Established Title: | Established |
| Established Date: | November 6, 1849 |
| Unit Pref: | Imperial |
| Area Total Sq Mi: | 36.98 |
| Area Land Sq Mi: | 36.98 |
| Area Water Sq Mi: | 0.00 |
| Area Water Percent: | 0.01 |
| Population As Of: | 2020 |
| Population Total: | 568 |
| Population Density Sq Mi: | auto |
| Elevation M: | 164 |
| Elevation Ft: | 538 |
| Coordinates: | 40.3272°N -90.9675°W |
| Timezone: | CST |
| Utc Offset: | -6 |
| Timezone Dst: | CDT |
| Utc Offset Dst: | -5 |
| Postal Code Type: | ZIP codes |
| Postal Code: | 62316, 62321, 62367 |
| Blank Name: | FIPS code |
| Blank Info: | 17-067-67054 |
Saint Mary's Township is one of twenty-four townships in Hancock County, Illinois, USA. As of the 2010 census, its population was 568 and it contained 295 housing units.[1]
According to the 2021 census gazetteer files, St. Mary Township has a total area of 36.98sqmi, of which 36.98sqmi (or 99.99%) is land and 0sqmi (or 0.01%) is water.[2]
As of the 2020 census there were 568 people, 278 households, and 184 families residing in the township. The population density was 15.36PD/sqmi. There were 295 housing units at an average density of 7.98/sqmi. The racial makeup of the township was 97.36% White, 0.70% African American, 0.00% Native American, 0.35% Asian, 0.00% Pacific Islander, 0.53% from other races, and 1.06% from two or more races. Hispanic or Latino of any race were 0.88% of the population.
There were 278 households, out of which 20.90% had children under the age of 18 living with them, 57.19% were married couples living together, 5.04% had a female householder with no spouse present, and 33.81% were non-families. 30.20% of all households were made up of individuals, and 9.40% had someone living alone who was 65 years of age or older. The average household size was 2.23 and the average family size was 2.78.
The township's age distribution consisted of 15.6% under the age of 18, 11.3% from 18 to 24, 11.5% from 25 to 44, 30.4% from 45 to 64, and 31.2% who were 65 years of age or older. The median age was 51.2 years. For every 100 females, there were 132.6 males. For every 100 females age 18 and over, there were 130.8 males.
The median income for a household in the township was $45,833, and the median income for a family was $58,333. Males had a median income of $40,179 versus $34,063 for females. The per capita income for the township was $25,668. About 12.0% of families and 15.0% of the population were below the poverty line, including 39.2% of those under age 18 and 10.3% of those age 65 or over.