Advertising thermometers first appeared in the 1900s and were widespread in the United States by the 1920s. Intended to be hung outside, the earliest were made of metals like tin, plus wood. Eventually, they were also made out of the same material as porcelain signs. Common shapes for vintage advertising thermometers include round signs with hands like a clock, and vertical rectangular or die-cut signs with a mercury meter in the middle. The sign might be cut into an ovoid “cigar-shape” or a soda bottle. At the turn of the century, America was largely a rural nation, and it was difficult for advertisers to get the word out about their products. Most farming communities might not have a newspaper or even a train station nearby, so the local general store or diner would be the place people would gather to hear the latest news and gossip. Traveling salesmen would often come bearing gifts, like beautiful tin or porcelain signs shilling their products, for the owner of the café, gas station, or the five-and-dime to hang at their establishment. Companies like Coca-Cola figured out that if an advertisement were also a utilitarian object, such as a chalkboard, a light fixture, or a clock, it would stay up at the store longer than an ordinary sign. That’s why companies of all stripes began producing outdoor advertising thermometers in the 1920s. They were made by beverage, food, tobacco, automotive, and agricultural firms, as well as the health-care industry. These were hugely popular in rural areas, because knowing the temperature, as well as the wind direction, was key to predicting the weather. Big brands like Coca-Cola, Pepsi, Dr. Pepper, NeHi, Mail Pouch Tobacco, Hills Bros. Coffee, John Deere, Pabst, Sunbeam Bread, Nesbitt's, Exide Batteries, Royal Crown Cola, and Hire's Root Beer all produced metal thermometers. The earlier wooden thermometers tend to be for rare local brands. Some are as small as circles 9 to 12 inches in diameter, while other rectangular versions were as big as 6 feet high. But the most common height for a rectangular thermometer is 16 to 17 inches. It was also typical to see popular cartoon characters, like Betty Boop, on these thermometers. From around 1940 to 1976, the Pam Clock Company made many of the advertising thermometers for major companies, as well as advertising clocks. The 1940s was also the time that advertisers started making drugstore advertising thermometers out of Masonite. In the 1980s, as antique thermometers grew in popularity as a collectible to hang on one’s wall at home, some companies started reproducing vintage thermometers to sell as retro-style décor. While they aren’t original, many of these are considered vintage now. In recent years, particularly old and rare advertising thermometers sold for as much as $1,000 to $2,000. The most valuable antique advertising thermometers have a working temperature gauge. Even though condition is an important factor in an advertising thermometer’s value, collectors should be wary of any advertising thermometer that doesn’t show signs of wear from being hung outside—it could be fake. Same goes if a dealer has several of the same advertising thermometers for sale.