Here is what I found on the net about the history of this holiday:
"According to church tradition St. Valentine was a Bishop near Rome in about the year 270 A.D. At that time the Roman Emperor Claudius II issued an edict forbidding marriage. When Claudius became the emperor, he felt that married men were more emotionally attached to their families, and thus, will not make good soldiers. So to assure quality soldiers, he banned marriage completely.
Valentine, a Bishop , in accordance with God's Word regarding the Sacrament of Marriage, and upon seeing the trauma of young lovers throughout Rome, met them in a secret place despite the "law" of the land, and joined them in the Sacrament of Matrimony. Emperor Claudius learned of this "Friend of Lovers", and had him arrested. The Emperor was impressed with the young Bishop's dignity and conviction, and attempted to convert him to worshiping the Roman Gods, to save him from certain execution. Valentine refused to even recognize Roman Gods. Valentine even attempted to convert the Emperor to Christianity, knowing the consequences fully.
While Valentine was in prison awaiting his fate of execution, he met his jailor, Asterius. The jailor had a blind daughter. Asterius requested that Valentine heal his daughter of her blindness. God restored the sight of Asterius' daughter through Valentine, a very faithful man - it was a miracle !! Just before his execution, Valentine asked for writing supplies from his jailor. He penned a farewell message to the jailor's daughter "From Your Valentine, a phrase that lived ever after. On February 24, 270, Valentine was executed. "
(Click here for full story: http://www.theholidayspot.com/valentine/history_of_valentine.htm)