The hill was presumably on Angel Island or built on it after the floating continent was lifted into the sky due in part to the Fire Ants' efforts in chewing away the the rock binding the island to Downunda. From that time forward the Fire Ants would observe their Echidna neighbors, providing aid but often anonymously. The first to change this would be Christopheles, who was appointed by the council to aid Edmund, the first Guardian, during the Angel Island Civil War.
Like many locales and inhabitants of Angel Island, the Fire-Ant Hill suffered greatly as a result of Dr. Ivo "Eggman" Robotnik's occupation of the island with the Dingo Regime under his command. This resulted in the fall of the Fire Ant Queendom, with the possible loss of both Queen and hill. (CSE)