According to History of Valentine’s Day, the true origin of St. Valentine’s Day is still murky. However, the Catholic Church does recognizes at least two different saints named Valentine or Valentinus. One of these legends states that Valentine was a third century priest in Rome. During that time, Emperor Claudius II outlawed marriage for young men, believing single men made better soldiers than married men with families. Deeming the decree unjust, Valentine continued to perform marriages for young couples in secret. When Claudius discovered Valentine’s secret weddings, he ordered Valentine’s beheading.

The second legend about St. Valentine’s life suggests he attempted to aid Christians in escaping the harsh Roman prisons, but instead was caught and incarcerated himself. According to the story, Valentine actually sent the first “valentine” card to a young girl he fell in love with. Who this girl actually was is still up to debate, but several sources suggest she was possibly the jailer’s daughter who visited him during his confinement. It is alleged that before his execution, he signed a letter “From your Valentine”—the expression stuck and is still widely used today.

Although St. Valentine’s true history is still ambiguous, all the legends portray his sympathy, heroism, and romance. These qualities led him to becoming one of the most popular saints in England and France by the Middle Ages.

St. Valentine’s popularity granted him his own holiday, however the reasoning behind the holiday is still unclear. Some believe Valentine’s Day is celebrated in February to memorialize the Saint’s burial, which most likely occurred about 270 A.D. Others claim that the Catholic Church placed the holiday in February, right in the middle of the pagan celebration of Lupercalia, a festival to purify the city and avert evil spirits. Many claim St. Valentine’s Day was held in February in an effort to “Christianize” the pagan celebration.

At the end of the fifth century, however, Lupercalia was eventually deemed un-Christian and was outlawed. Pope Gelasius officially declared Feb. 14 St. Valentine’s Day to celebrate the life of Valentine. Slowly over time the holiday became associated with love, due to the common belief that, in France and England, Feb. 14 was the beginning of the birds’ mating season.

Although the romantic holiday dates back to the Middle Ages, written valentine messages did not catch on until the year 1400. The oldest documented Valentine is a poem written in 1415 by Charles, Duke of Orleans, to his wife during his imprisonment in the Tower of London following his capture in the Battle of Agincourt. It is believed that several years later, King Henry V hired the writer John Lydgate to compose valentine letters to his wife Catherine of Valois.

The tradition spread to the United States during the early 1700s, but wasn’t until 1840 when Esther A. Howland began to sell the first mass-produced valentines in America. Known as the “Mother of Valentine”, Howland created elaborate cards with lace, ribbons and colorful pictures. According to the Greeting Card Association, an estimated 1 billion Valentine’s cards are sent on Feb. 14 each year.