Horta is a part of Fayal Islands in the Azores archipelago which is 930 miles west of Portugal in the Atlantic Ocean. Portugal was great colonial power till 1975 after which it gave away its colonies. Azores is now an autonomous region of Portugal.
Two sets of King Carlos definitive stamps were released by Horta in 1892-93 and 1897-1905 when it was under Azores. Portugal collectors and classic stamp collectors are always on the hunt for these stamps. 34 stamps were issued by the country. The first set has an officially listed value of $261 in unused hinged condition and the second set has a value of $124.35 in unused hinged condition. Stamps were printed on soft paper so you might find many with missing perforations or thins. Covers and stamps in mint never-hinged condition are rare to find.