[6] Knox City is located at in eastern Knox County at the intersection of Missouri Route 6 with routes E and V. Edina is approximately 8.5 miles to the west and La Belle is five miles to the east-southeast in adjacent Lewis County.

[7] According to the United States Census Bureau, the city has a total area of 0.21 square miles (0.54 km2), all land.

There were 126 housing units at an average density of 600.0 per square mile (231.7/km2).

39.4% of all households were made up of individuals, and 19.3% had someone living alone who was 65 years of age or older.

40.9% of all households were made up of individuals, and 24.3% had someone living alone who was 65 years of age or older.

About 8.5% of families and 16.0% of the population were below the poverty line, including 5.0% of those under the age of eighteen and 36.7% of those 65 or over.