In the 1880s, the population of Adelaida was approximately 500, supported by the prospering Klau and Buena Vista mercury mines. The town boasted a community center, saloon, dance hall, general store, and four schools. The population increased further in 1898 with an influx of Mennonite settlers. The Adelaida School, located near the entrance to the Osgood Ranch on Chimney Rock Road, was built in 1917. It is still standing, although has been vacant since 1964. This school and the Klau Mine Road cemetery are all that is left of old Adelaida. Although the quicksilver mines were in operation into the 1970s, most of the local businesses had long since relocated to Paso Robles.