Altamont is a town in and the county seat of Grundy County, Tennessee, United States. The population was 1,117 at the 2020 census. Altamont was established in 1848 as a county seat for Grundy County, which had been created in 1844. General Adrian Northcutt, a prominent local farmer and military officer, was the prime advocate for the site's selection. T…Altamont is a town in and the county seat of Grundy County, Tennessee, United States. The population was 1,117 at the 2020 census. Altamont was established in 1848 as a county seat for Grundy County, which had been created in 1844. General Adrian Northcutt, a prominent local farmer and military officer, was the prime advocate for the site's selection. The town's name comes from combining alto and mont. Although the Civil War somewhat stunted the town's growth, by 1870 Altamont's population had grown to 217.