Mount Ida is a city in and the county seat of Montgomery County, Arkansas, United States. Founded in 1842, the city saw a silver boom in the 1880s bring early prosperity and economic development to the area. Today, the economy is largely ranching, poultry farming, silviculture, and tourism around Lake Ouachita. It is known as the quartz crystal capital of the U.S. and is known worldwide for its quartz deposits. The population was 996 as of the 2020 census.