Halidom was a small principality in Munchkin Country ruled by King Herald 64th and Queen Farthingale. It had always been protected by three magic Circlets, until they went missing. Its crown prince, Gules, went on a journey to get them back. (Merry Go Round in Oz)

Before the loss of its Circlets, Halidom had a University of Genealogy and a thriving industry in coats of arms, which it exported to all the small kingdoms of Oz. With the restoration of the Circlets, these enterprises were probably revived. The 1963 issue of The Ozmapolitan describes and illustrates examples of Halidom coats of arms produced for the Tin Woodman and the Scarecrow.