U.S. Geological Survey, Rock Magnetics Laboratory, 345 Middlefield Road, Menlo Park, San Mateo County, CA

Significance: The temporary building, which was originally a temporary military hospital, became, in 1959, the home of the Rock Magnetics Laboratory and the site of revolutionary research in the field of earth sciences. This research, carried out by Richard Doell, Allan Cox, and Brent Dalrymple, culminated in 1966 with a time scale for reversals of the earth's magnetic field. This discovery contributed significantly to evidence in favor of plate tectonics. The Rock Magnetics Laboratory was designated a National Historic Landmark on October 12, 1994. Designation as a National Historic Landmark automatically places the property in the National Register of Historic Places. The period of significance for the Rock Magnetics Laboratory is from 1959 to 1966
Survey number: HAER CA-173
Building/structure dates: after. 1942- before. 1955 Initial Construction
Building/structure dates: after. 1958- before. 1967 Subsequent Work
Building/structure dates: 1997 Demolished