The onions were first grown near Vidalia, Georgia, in the early 1930s. It is an unusually sweet variety of onion, due to the low amount of sulfur in the soil in which the onions are grown.
Georgia's state legislature passed the "Vidalia Onion Act of 1986" which authorized a trademark for "Vidalia Onions" and limits the production area to Georgia or any subset as defined by the state's Commissioner of Agriculture.
The Vidalia onion was named Georgia's official state vegetable in 1990.
Vidalia onion. Wikipedia.