[4] According to the United States Census Bureau, the city has a total area of 0.86 square miles (2.23 km2), all land.

There were 126 housing units at an average density of 146.5 per square mile (56.6/km2).

25.2% of all households were made up of individuals, and 13.4% had someone living alone who was 65 years of age or older.

There were 98 housing units at an average density of 103.2 per square mile (39.8/km2).

17.9% of all households were made up of individuals, and 12.6% had someone living alone who was 65 years of age or older.

About 4.8% of families and 8.3% of the population were below the poverty line, including none of those under the age of eighteen and 41.7% of those 65 or over.

St. Martin is the home to a large bikers gathering every summer sponsored by Doochie's Bad Company Bar.

The Martins recently added lights to their baseball field, allowing them to play at night.