Alturas is a city and the county seat of Modoc County, California. Located in the Shasta Cascade region of Northern California, the city had a p…Alturas is a city and the county seat of Modoc County, California. Located in the Shasta Cascade region of Northern California, the city had a population of 2,715 at the 2020 census. Alturas is located at the confluence of the south and north forks of the Pit River, east of the center of Modoc County, at an elevation of 4,370 feet. Alturas is one of the largest cities in the region and a local economic hub.