Lyon Mountain is a hamlet and census-designated place located in the town of Standish in Clinton County, New York, United States. The population was 423 at the 2010 census.
The hamlet of Lyon Mountain is located at 44°43′44″N 73°54′28″W / 44.72889°N 73.90778°W / 44.72889; -73.90778 (44.728863, -73.907905). According to the United States Census Bureau, the CDP has a total area of 10.2 square miles (26.3 km), all land.
Lyon Mountain is on New York State Route 374, which leads east 12 miles (19 km) to Dannemora village and northwest 17 miles (27 km) to Chateaugay.
As of the census of 2000, there were 458 people, 214 households, and 129 families residing in the hamlet. The population density was 45.0 per square mile (17.4/km²). There were 234 housing units at an average density of 23.0/sq mi (8.9/km²). The racial makeup of the CDP was 95.85% White, 0.22% African American, 1.09% Native American, 0.22% Pacific Islander, and 2.62% from two or more races.
There were 214 households out of which 22.0% had children under the age of 18 living with them, 47.2% were married couples living together, 8.9% had a female householder with no husband present, and 39.3% were non-families. 36.0% of all households were made up of individuals and 22.9% had someone living alone who was 65 years of age or older. The average household size was 2.14 and the average family size was 2.72.
In the community, the population was spread out with 18.3% under the age of 18, 5.7% from 18 to 24, 22.5% from 25 to 44, 30.6% from 45 to 64, and 22.9% who were 65 years of age or older. The median age was 46 years. For every 100 females, there were 93.2 males. For every 100 females age 18 and over, there were 85.1 males.
The median income for a household in the village was $25,000, and the median income for a family was $41,250. Males had a median income of $39,688 versus $20,250 for females. The per capita income for the CDP was $16,776. About 14.8% of families and 14.1% of the population were below the poverty line, including 21.7% of those under age 18 and 7.7% of those age 65 or over.