Valentine's Day as we know it today had it's beginning from ancient Christian and Roman traditions. Legends state that is had originated from an ancient Roman festival call Lupercalis or Lupercalia. It was a fertility celebration that was observed annually on February 15th. Through time just the same as many pagan traditions were, Lupercalis was 'adopted' into the Christian beliefs to convert the Pagans.
Pope Gelasius is credited with the conversion of Lupercalia into a Christian festival day in 496 AD and set it's date from February 15th to one day earlier the 14th. Of course, he had to have a Christian deity to replace the Pagan one, so he choose that the day of feasting would be in honor of St.Valentine who was a Roman martyr that had lived in the 3rd century.
Who was St. Valentine? According to the pages of recorded history, we find that there were at least 3 saints by the name of Valentine. One was a priest in Rome, who lived around 270 AD and was very dis-favored by the Roman Emperor Claudius II. Another was a bishop of Interamna ( modern Terni ) in 197 AD. He was martyred during the rule of Emperor Aurilian. He was / is buried on the Via Flaminia. At the Basilica of Saint Valentine are relics of this particular saint.
The third, not much is known about him except that he died in Africa.
The first Valentine is the one that most people give credit to, St. Valentine of Rome.
Around 270 AD Rome was in turmoil with their government falling apart from the inside out, the border of their once mighty kingdom was being bombarded by Huns, Turks, Gauls, Slavs and the Mongolians so Claudius needed more men to fill his armies. As the necessity of young men began to grow, Claudius felt that for them to be more focus on their duty as a soldier, they were not to be married. He passed a law forbidding the act of marriage for any of the young soldiers.
St. Valentine didn't agree with the law and thought it was unfair. During time, when a lot of the young men thought about marrying someone they would go to St. Valentine. He would then marry them in secret. Valentine became the 'friend of lovers' and of course word got out and eventual fell upon Claudius' ears. Claudius had St. Valentine arrested.
As many saints do, Valentine was thought to have healing abilities. While he was in jail, his jailer, Asterius asked him to please heal his daughter who was blind. Valentine fulfilled the request.
When Claudius II met Valentine he was very impressed by him. The two got into a conversation about the ban on marriage in which Valentine still held to his faith. During this conversation, Claudius tried to convert Valentine to the Roman Gods. Valentine still refused and in return tried to convert Claudius to the Christian path. This angered Claudius very much, so much that he had Valentine executed.
According to legend, during his time in the Roman jail, Valentine fell in love with a jailer's daughter. Some legends says that is was the blind daughter of Asterius. Before his execution, Valentine asked for a pen and paper so he could write a farewell to her. Part of the farewell was "from your Valentine" and it has stuck ever sense. It is believed he was executed on February 14th, 270 AD which became a day for all lovers. The Romans began to annually give hand written greetings to their lovers and called them Valentines.
During the Middle Ages, St. Valentine became one of the most popular saints in England and France which pushed the celebration of February the 14th as the day of love and romance even further.
In the 14th Century, Chaucer and his friends which became known as Chaucer's Circle, started sending each other poems of love. The first Valentine card? Chaucer would use images of birds to represent lovers in his poems.
The Victorian age came around and gave St. Valentine's Day another push. People started using ribbons, lace and images of love such as hearts on their cards of greetings.
In the 18th Century, gift giving and exchanging homemade cards became common in England and when the early American colonist came to Americas, the tradition came with them.
One of the earliest known Valentine was sent in 1415 by Charles, Duke of Orleans. It was to his wife while he was imprisoned in the Tower of London. The card is now in the British Museum.
Eventually the Saint was dropped from the Lover's Day to what we know it as today, Valentine's Day.