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Morton Salt has long been known for its famous logo featuring the iconic “umbrella girl” — dressed all in yellow and walking in the rain as salt pours freely from a container of Morton’s — over the phrase “When It Rains, It Pours.”

She first appeared in 1914, in the days when table salt tended to clump up when exposed to humidity. The problem was solved by the Morton Salt Company when it added magnesium carbonate, an absorbing agent, to its product. The new salt would flow freely in even the most humid weather.

But Morton introduced a more important innovation in 1924. Scientists had discovered that common thyroid disorders could be remedied with iodine. People in the Great Lakes region and the Pacific Northwest, which had too little iodine in the ecosystem, were prone to developing enlarged thyroids, or goiters. Iodine shortage also affected the brain, leading to difficulty in learning or remembering.

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Readers might have thought the 1927 ad was overstating the benefits of iodized salt. But the incidence of goiters dropped significantly after iodization, and the average IQ rose 15 points in areas where iodized salt had been introduced, and 3.5 points nationally.

This article is featured in the May/June 2019 issue of The Saturday Evening Post. Subscribe to the magazine for more art, inspiring stories, fiction, humor, and features from our archives.