martyrdom · 304 · Rome
Everything told about Agnes in narrative — the suitor she refused, the brothel she was sent to, the hair that grew to cover her, the fire that would not burn — comes from passions written a century and more after her death, and they do not agree with each other. What is solid is earlier and plainer. She is in the Depositio Martyrum of 354, on 21 January, with her cemetery on the Via Nomentana named; Constantina, the daughter of Constantine, built a basilica over the grave before 354; Damasus set an inscription there; and Ambrose and Prudentius both wrote about her within seventy to a hundred years, as of someone every Roman child knew. She is one of only seven women named in the Roman canon of the mass. So the shape of the record is unusual and worth stating plainly: the cult is documented very early and very well, and the story is late and legendary, and those are two different claims about the same girl.
How much can be known about a girl killed at twelve?
That she existed, that she was buried on the Nomentana, and that Rome never stopped going there.