- Herlong is a small unincorporated community located in Lassen County, California, United States. It is situated in the northeastern part of the state, near the Nevada border. Herlong is primarily known for the presence of the Sierra Army Depot, a military installation that stores, renovates, and maintains various types of equipment for the United States Army. The community itself mainly consists of housing for military personnel and their families. Overall, Herlong offers a quiet and rural lifestyle with limited amenities and services. The nearest larger towns are Susanville, approximately 20 miles to the south, and Reno, Nevada, about 65 miles to the northeast.