This is a bracket from the Vertical Test Stand No. 1 (VTS-1) of the Santa Susana Field Laboratory, of Rocketdyne, in the Santa Susana Mountains, California. The VTS-1 was an important site used by Rocketdyne and its predecessor from the 1950s for the testing of the U.S.'s first large-scale liquid propellant rocket engines, starting with the Redstone missile engine.
This engine evolved in the engines for the Thor, Jupiter, and Atlas missiles, the engines for the Saturn V launch vehicle that took men to the Moon, and the Shuttle Main Engine. The VTS-1 was demolished in 1996, with the sign and other parts retrieved later. This object was donated to the Smithsonian by Rocketdyne.