St. Valentine’s Day originated from a pagan festival celebrated by the ancient Romans on February 15, which was known as Lupercalia. The purpose of Lupercalia was to honor the Faunus, the god of agriculture, along with the founders of Rome, Romulus and Remus, and to promote fertility for the coming year. After animals were sacrificed earlier in the day, the young women would place their names in an urn. Every bachelor would choose a name at random, and that woman would become his partner for the next year. These partnerships often resulted in marriages.

Lupercalia was still taking place during the rise of Christianity, and was not outlawed until the end of the fifth century. At that time, Pope Gelasius declared that the fourteenth of February would be the feast day of Saint Valentine, the patron saint of lovers and engaged couples.

The Catholic Church recognizes three or more saints named Valentine or Valentinus, and it is unknown which one of them Pope Gelasius was referring to. All of them were martyred, and the holiday’s two most likely namesakes may have been the same person, as both of them lived during the reign of the same emperor and died on the same day.

The first Saint Valentine was a priest who lived in Rome during the reign of Emperor Claudius II, who was also known as Claudius the Cruel. Claudius was having difficulty recruiting men to serve in the bloody campaigns that Rome was involved in at the time. He attributed this to the fact that most Roman men were attached to their wives and families; as a result, he outlawed marriage for young men. Saint Valentine decided that this was unfair and proceeded to marry young couples in secret. Eventually, Claudius found out about his activities and sentenced Valentine to death.

Another Valentine was a Christian who was imprisoned for his beliefs. At some point during his time in prison, he fell in love with his jailor’s blind daughter. He prayed for her, and she regained her sight. Days before his execution, he sent the jailor’s daughter a note and closed it with “From your Valentine”, which is still used on greeting cards today.

The feast day of St. Valentine was not associated with love until the Middle Ages, when most of the people in France and England believed that the mating season of birds began on February 14. Around the same time, Valentine’s Day greetings became popular. The first written valentines appeared after 1400, the oldest of which was written in 1415 by Charles, Duke of Orleans.

Americans started to exchange hand made valentines in the 1700s. In the 1840s, Esther Howland began selling the first mass produced valentines. Today, about one billion Valentine’s Day cards are sent every year.