Helena - Background:
Helena (Flavia Iulia Helena), known as St. Helena and Helena Augusta, lived from about 249-329 A.D. She is thought to have come from Drepanum, in the Roman province of Bithynia, because her son, the Emperor Constantine, renamed Drepanum Helenopolis after her. Helena's origins are obscure, but she is thought to have worked in a tavern where she met the soldier Flavius Valerius Constantius, who became her husband. Her date of death is approximate and based on Eusebius saying she was 80 years old.
Constantius and Helena had at least one child, Constantine, born 272 or 274. This is the Constantine who converted the Roman Empire to Christianity. The couple remained married for about 20 years until the time of Diocletian in 284. Then, when the Empire was split in two and Constantius was made Caesar, he left Helena to marry the daughter of Emperor Maximianus, Theodora.
Re-emergence of Helena:
When Constantine became emperor, he installed his mother, Helena, at his court, where she was titled Nobilissma Femina. In 324, after Constantine's defeat of Licinus, Constantine conferred on his mother the honorary title of Augusta.
Religious Significance of St. Helena:
Main Sources: [web.mac.com/heraklia/Dominae/] Feminae Romanae Helena Augusta, c. 249-329 AD
DIR Helena Augusta