Rattlesnake Mountain (Native American name Lalíik meaning "land above the water") is a 3,531 ft (1,060 m) windswept treeless ridge overlooking the Hanford nuclear site.

[6] In 1943, Rattlesnake Mountain was seized by the United States government under eminent domain and became a buffer zone for the nuclear project at the Hanford site.

Observatory operations were directed by a local nonprofit group founded by scientists and engineers from the Pacific Northwest National Laboratory at Hanford.

[8] It was announced 14 March 2008 that the Department of Energy would not renew the permit, license or easements for the observatory or most of the other entities that maintain communication equipment on the mountain.

[13] Access was expected to begin in Fall 2019,[14] but it was still closed in October 2020 as the Fish and Wildlife Service has not released a final environmental study amid continued consultations.