“History of salt iodination
The iodination of salt was first suggested in 1833 by French scientist Jean Baptiste Boussingault (1802–1887):
“The iodination of salt was first suggested by Boussingault, who lived for many years in Colombia, South America, and discovered that the local people benefit from salt obtained from an abandoned mine in Guaca, Antioquia. In 1825 Boussingault analyzed this salt and found large quantities of iodine. Subsequently, in 1833 he suggested that iodized salt be used for the prevention of goiter.” [1]
It would not be, however, until 1924 that iodination of salt became public policy.
Iodine, in fact, was the very first food element to be commercially added to food as a supplement — in Michigan, in 1924. Salt was chosen because it was the most commonly used foodstuff that iodine could be added to easily and inexpensively. The other way that consumers get iodine as an additive is through dairy and meat: iodine is added to animal feed. Natural ways to get iodine are through eating seafood and kelp (by the way, the iodine in sea salt is so minuscule that it is of no use to your body.) “
https://www.cooksinfo.com/salt#History_of_salt_iodination
I use Sea Salt and when I first started buying it, it didn’t have iodine. Now it says it does so they might have started adding it to it too?