The concept for the poem originated from a traumatic incident in Frost’s early childhood, when he was five or six years old. As an adult, Frost shared the story with several people. Although the versions differ slightly in their details, the core narrative is consistent. Here, Frost recounts what happened to his friend, Louis Mertins:

I was very small and impressionable—a child full of imagination and phobias. I watched the big waves coming in, blown by the wind. I recall that I was playing on the sand with a long black seaweed, using it for a whip. The sky must have clouded up, and night began to come on. The sea seemed to rise up and threaten me. I got scared, imagining that my mother and father, who were somewhere about, had gone away and left me by myself in danger of my life. I was all alone with the ocean water rising higher and higher. I was fascinated and terrorized watching the sea; for it came to me that we were all doomed to be engulfed and swept away. Long years after I remembered the occasion vividly, the feeling which overwhelmed me, and wrote my poem, “Once by the Pacific” (Quoted in Holland, Norman N.