“What Must a Fairy’s Dream Be?” was entered for copyright deposit by W. C. Peters, Cincinnati on October 18, 1847.

According to Evelyn Foster Mornweck’s The Chronicles of Stephen Foster’s Family:

“What Must a Fairy's Dream Be?” was copyrighted by W. C. Peters on October 18, 1847, and was dedicated by Stephen to Mary H. Irwin, the daughter of the Hon. Thomas Irwin, who lived at the corner of Grant and Diamond streets, Pittsburgh. Mary was one of the pretty girls admired by the Foster boys. The verses of “What Must a Fairy’s Dream Be?” are of a style that must have delighted Stephen’s romantic mother.

Later she writes:

Another of Stephen’s compositions, “What Must a Fairy’s Dream Be?” had been sung at the Eagle Saloon on August 19, 1847, two months before it was entered for copyright by Mr. Peters. It was sung by Miss Bruce in a grand “extraordinary musical entertainment” on the evening of August 19, and, the program states, for the first time. It is likely that the vocalists brought the manuscript of this song, and also a copy of “Oh! Susanna” with them from Cincinnati, having received them from Stephen himself.