Landaff is a town in Grafton County, New Hampshire, United States. At the 2010 census, the town population was 415.
According to the United States Census Bureau, the town has a total area of 28.5 square miles (74 km), of which 28.4 sq mi (74 km) is land and 0.1 sq mi (0.26 km) is water, comprising 0.25% of the town. The highest point in Landaff is the summit of Moody Ledge, at 2,326 feet (709 m) above sea level. The Ammonoosuc River defines part of the northwestern boundary of the town, and the Wild Ammonoosuc River flows through the southern part of the town. Landaff lies fully within the Connecticut River watershed.
The southern half of the town is in the White Mountain National Forest, accessible via Cobble Hill Trail and Ore Hill Trail from the north. Natural features of Landaff include many viewsheds, mountain summits, wetlands, undeveloped woodland and farm land. The main bodies of water in town are Chandler Pond, Jericho Pond and Gordon Pond.
As of the census of 2000, there were 378 people, 154 households, and 107 families residing in the town. The population density was 13.3 people per square mile (5.1/km²). There were 214 housing units at an average density of 7.5 per square mile (2.9/km²). The racial makeup of the town was 96.56% White, 0.26% Native American, and 3.17% from two or more races. Hispanic or Latino of any race were 0.79% of the population.
There were 154 households out of which 29.2% had children under the age of 18 living with them, 61.7% were married couples living together, 6.5% had a female householder with no husband present, and 29.9% were non-families. 21.4% of all households were made up of individuals and 11.0% had someone living alone who was 65 years of age or older. The average household size was 2.45 and the average family size was 2.88.
In the town, the population was spread out with 23.8% under the age of 18, 5.6% from 18 to 24, 27.0% from 25 to 44, 28.8% from 45 to 64, and 14.8% who were 65 years of age or older. The median age was 42 years. For every 100 females, there were 93.8 males. For every 100 females age 18 and over, there were 95.9 males.
The median income for a household in the town was $41,964, and the median income for a family was $48,500. Males had a median income of $35,156 versus $23,438 for females. The per capita income for the town was $18,033. About 6.9% of families and 7.1% of the population were below the poverty line, including 5.7% of those under age 18 and 12.9% of those age 65 or over.