Illinois Route 41 passes through the center of the village, leading north 6 miles (10 km) to Abingdon and 17 miles (27 km) to Galesburg, the county seat.

Illinois Route 116 follows the northern border of the village, leading east 8 miles (13 km) to London Mills and west 13 miles (21 km) to Roseville.

According to the 2010 census, St. Augustine has a total area of 0.63 square miles (1.63 km2), all land.

27.9% of all households were made up of individuals, and 14.7% had someone living alone who was 65 years of age or older.

About 4.3% of families and 5.6% of the population were below the poverty line, including none of those under the age of eighteen or sixty five or over.