St. Lucas is a city in Fayette County, Iowa, United States.

[4] According to the United States Census Bureau, the city has a total area of 0.27 square miles (0.70 km2), all land.

There were 84 housing units at an average density of 330.5 per square mile (127.6/km2).

There were 85 housing units at an average density of 314.8 per square mile (121.5/km2).

35.6% of all households were made up of individuals, and 20.6% had someone living alone who was 65 years of age or older.

30.1% of all households were made up of individuals, and 24.1% had someone living alone who was 65 years of age or older.

About 8.3% of families and 9.5% of the population were below the poverty line, including none of those under the age of eighteen and 21.4% of those 65 or over.

[10] Father Aloysius Schmitt (1909–1941), the first chaplain to die in World War II, on board the USS Oklahoma during the Pearl Harbor bombing[11]