Thornburg is a village in Keokuk County, Iowa, United States.

The Burlington, Cedar Rapids and Northern Railway built a 66-mile branch to What Cheer via Thornburg in 1879.

[4] The town was founded by the railroad and named in memory of Major Thomas T. Thornburgh, who died in the Meeker Massacre.

[7] According to the United States Census Bureau, the city has a total area of 0.20 square miles (0.52 km2), all of it land.

There were 24 housing units at an average density of 120.5 per square mile (46.5/km2).

Hispanic or Latino persons of any race comprised 0.0% of the population.

There were 29 housing units at an average density of 145.0 per square mile (56.0/km2).

There were 36 housing units at an average density of 183.0 per square mile (70.7/km2).

There were 9.1% of families and 4.9% of the population living below the poverty line, including no under eighteens and 50.0% of those over 64.