From "Roses are red, violets are blue" to something slightly more heartfelt, valentine cards are the yardstick of self worth every February.

The appeal is not a recent phenomenon, as showcased in "Be Mine Valentine," a profile of 150 years worth of valentines on display at the Warren County Historical Society Museum in Lebanon. The exhibit features more than 500 valentines from the WCHS's collection, from 1850s to present day.

"In the late 1800s, collecting valentine post cards became a passion," said museum director Victoria Tappy.

The popularization of the color lithograph, which allowed for bright hues and intricate pictures to be printed on the love letters, made the first valentines possible and started a furor over them, Tappy said.

Many early valentines were particularly ornate, and some in the collection are even hand-crafted.

The early 20th century saw manufacturers discover the merchandising possibilities inherent in valentine cards, and the museum's collection includes tie-ins for Buster Brown shoes and a Toledo-based spice company.

"Be Mine Valentine" runs through Feb. 19 at the WCHS, 105 S. Broadway.