Johnston Atoll was discovered by Americans in 1796, or the British in 1807, and was claimed by both the United States and the Kingdom of Hawaii in 1858; it was not, however, included in the state of Hawaii. U.S. companies exploited the island for guano until the 1880s. A bird sanctuary since the 1920s, the strategic island was under U.S. Navy control from 1934 and Air Force control after 1948. In the 1950s and 60s the United States conducted a series of nuclear tests there, causing some radioactive contamination of the atoll; the area was also a chemical and biological weapons storage and incineration site. Contaminated soil is now stored in a landfill.