This song came from poetry written in Jim Morrison's notebooks. He wrote it after splitting up with his girlfriend, Mary Werbelow, in the summer of 1965. Critic James Perone noted that the song's title is open to wide interpretations, and that the crystal ship "could just as easily represent sleep as a drug trip". He conceded that "in 1967 the latter would probably have been the more common interpretation". John Densmore responded by saying that although Morrison was aware that "crystal" is slang for methedrine, he "wrote 'The Crystal Ship' for Mary Werbelow, a girlfriend with whom he was breaking up: it was therefore intended as a goodbye love song." The song's title borrows from the 12th-century Irish Lebor na hUidre (Book of the Dun Cow) manuscript, a collection of stories compiled by about 1100 Irish monks around the 9th century. According to local Santa Barbara, California, lore, Morrison wrote the song after taking LSD on an Isla Vista beach one night as he stared at the blinking lights of an offshore oil rig named Platform Holly.