Haddam is a city in Washington County, Kansas, United States.

[5] According to the United States Census Bureau, the city has a total area of 0.35 square miles (0.91 km2), all land.

[6] The 2020 United States census counted 110 people, 33 households, and 24 families in Haddam.

There were 67 housing units at an average density of 195.3 per square mile (75.4/km2).

21.2% of households consisted of individuals and 12.1% had someone living alone who was 65 years of age or older.

The racial makeup of the city was 97.1% White, 1.0% Native American, and 1.9% from two or more races.

40.4% of all households were made up of individuals, and 30.7% had someone living alone who was 65 years of age or older.

The racial makeup of the city was 97.04% White, 1.18% Native American, and 1.78% from two or more races.

34.2% of all households were made up of individuals, and 21.9% had someone living alone who was 65 years of age or older.

About 9.1% of families and 16.3% of the population were below the poverty line, including 26.2% of those under the age of eighteen and 3.4% of those 65 or over.

In 1968, Haddam-Mahaska combined with Morrowville to form North Central Schools.