Site information:

The location given by OHP is Shake Ridge Road, 1 mi. W of Ram's Horn Grade, Volcano. The former plaque base was still there when I visited. Considering the text of the original plaque, this is probably the location of the observatory. There is nothing remaining at that site.

38.465852,-120.640374

Plaque information:

Main and Consolation Sts, Volcano

38.442798,-120.631366

Plaque text:

Astronomical Observatory

Here in Volcano in 1860, miner and amateur astronomer George Madeira built California's first astronomical observatory of record and operated it for two years. Using a three inch refractory telescope he studied sun and moon, stars and planets, and other glories of the heavens, including the great comet of 1861.

Plaque placed by the State Department of Parks and Recreation in cooperation with the Astronomical Societies of Stockton and Sacramento. Plaque first placed in 1968, revised and relocated in 2004.

OHP description:

On the knoll behind this marker George Madeira built the first amateur astronomical observatory of record in California. It was there that he discovered the Great Comet of 1861 with a three-inch refractor telescope.

Registered 10/6/1959