Esther Howland, the woman who produced the first commercial American valentines in the 1840s, sold a then mind-boggling $5,000 in cards during her first year of business. The valentine industry in the United States has been booming ever since. Today, over 1 billion valentine cards are sent in this country each year -- second in number only to Christmas cards, according to the Greeting Card Association. (The happy day is also celebrated in Canada, Mexico, the United Kingdom, France and Australia.)

Around 85 percent of all valentines are purchased by women. In addition to cards, there are millions of boxes of chocolates and bouquets of roses purchased (mostly by men) for the February 14 holiday.

When did the Valentine's Day frenzy begin? Scholars tell slightly different versions of the history of this popular holiday. In this article, we'll look at that history, with its Roman and Christian roots, as well as holiday traditions that have developed over the years. We'll also check out some old valentines and some new ones.