People had been exchanging handwritten notes on Valentine's Day for years. In 1846 Esther A. Rowland is credited with producing the first mass produced Valentine's Day Cards. They were heart shaped with embossed lace paper. They grew in popularity and within a few years were more popular than handwritten cards.
Today over 1 billion cards are exchanged on Valentine's Day making it the second most popular holiday for exchanging cards. Christmas is the number 1 holiday and Mother's Day is number 3, although more men by cards on Valentine's Day than any other day. Hallmark makes over 1500 different cards for different people on Valentine's Day.