The ampersand often appeared as a letter at the end of the Latin alphabet, as for example in Byrhtferð's list of letters from 1011. Similarly, & was regarded as the 27th letter of the English alphabet, as used by children (in the USA). An example may be seen in M. B. Moore's 1863 book "The Dixie Primer, for the Little Folks." In her 1859 novel Adam Bede, George Eliot refers to this when she makes Jacob Storey say: "He thought it [Z] had only been put to finish off th' alphabet like; though ampusand would ha' done as well, for what he could see."

Tsk, tsk. You'd think someone who worked in a library would know this sort of thing. Why, I learned it when I was a mere tad...wait, back then it WAS considered the last letter of the alphabet....