Na-Au-Say Township occupies the 6 mile square on the eastern edge of Kendall County, Illinois.

[3] The township's name was chosen by popular vote and came from the Native American village on the Aux Sable Creek (a branch of which flows through the township), which was named for a Potawatomi leader.

[4] According to the 2010 census, the township has a total area of 34.22 square miles (88.6 km2), all land.

[3] The population increased from 1,672 in 2000 to 8,145 due to developments, such as the Clublands, in the portions of Joliet and Plainfield that extend into the township.

The Township also has an elected Assessor, Clerk, and Highway Commissioner and Supervisor.