"Postcarditis" spread across the United States in 1903. With it, messages of love flowed, especially on Valentine's Day when "Postcarditis" and "Love Sickness" collide.

Here's the scoop... the first two decades of the 1900s are considered to be the "Golden Age of Postcards". The craze for sending and collecting postcards began in Europe in the 1890s and soon infected the United States. In 1896, rural delivery brought mail directly to farms; before, farmers had to make lengthy, periodic trips into town to pick up their mail. Rural delivery was enormously popular and greatly "enlarged the amount of mails handled," calling particular attention to "the enormous use of souvenir or picture post cards." The peak growth years of rural delivery — 1901 to 1909 — coincided with the postcard craze.

Women especially benefited from rural delivery and contributed to the growing popularity of postcards. A study of early 20th century postcards found that women sent three times as many as men and received four times as many. Many of the cards sent were holiday postcards, which emerged around 1903 and soon became so popular that Post Offices struggled to keep up
with delivery. On February 14, 1907, the Chicago Daily Tribune reported that "the valentine mail … is the greatest in the history of the local post office," with one-third consisting of "pictorial postal cards bearing cupids, hearts, flowers, and lovely maidens."

Here we see a potential love story playing out with reference to the musical, "Grease". Will she send it? What will he say next?