Sentinel, named for nearby Sentinel Peak, was established around 1880 as a station on the Southern Pacific Railroad. In 1943, after the US Army established two training camps nearby - Camps Hyder and Horn - Sentinel became the stopping point for many troops assigned there. Both camps closed in 1944, and Sentinel declined, losing its post office in 1960. Today, Sentinel is little more than a stopping point for travelers along Interstate 8. The small hamlet has a few houses, a service station, and even an elementary school.