St. Kilda is actually made up of four different islands called Hirta, Dun, Soay, and Boreray. The islands were formed as te result of oceanic eruptions 52 to 65 million years ago. The island was named a UNESCO world heritage site back in 1986. This includes its birds, animals, and the surrounding sea life.
The islands are thought to have been inhabited 7,000 years ago. Harsh storms during the 20th century lead to the residents of the island asking to be resettled by the British government in 1930.