Thayer is a city in Union County, Iowa, United States.

[3] According to the United States Census Bureau, the city has a total area of 0.09 square miles (0.23 km2), all land.

There were 22 housing units at an average density of 154.3 per square mile (59.6/km2).

There were 29 housing units at an average density of 322.2 per square mile (124.4/km2).

33.3% of all households were made up of individuals, and 4.2% had someone living alone who was 65 years of age or older.

There were 35 housing units at an average density of 356.7 per square mile (137.7/km2).

26.9% of all households were made up of individuals, and 15.4% had someone living alone who was 65 years of age or older.

Out of the total population, none of those under the age of 18 and 25.0% of those 65 and older were living below the poverty line.