Haddam is a city in Washington County, Kansas, United States. The population was 169 at the 2000 census.
Haddam is located at 39°51′23″N 97°18′10″W / 39.85639°N 97.30278°W / 39.85639; -97.30278 (39.856335, -97.302865). According to the United States Census Bureau, the city has a total area of 0.3 square miles (0.9 km²), all of it land.
As of the census of 2000, there were 169 people, 73 households, and 48 families residing in the city. The population density was 487.7 people per square mile (186.4/km²). There were 96 housing units at an average density of 277.0 per square mile (105.9/km²). The racial makeup of the city was 97.04% White, 1.18% Native American, and 1.78% from two or more races. Hispanic or Latino of any race were 0.59% of the population.