Cadiz traces its beginning to the establishment of a trading settlement in a place known as Cadiz Viejo, near the bank of the river Hitalon.
According to historical records, the settlement was named Valdevieso, in honor of the founder Don Manuel Valdevieso y Morquecho, who was then Alcalde Mayor of Negros. Later, it was renamed Cadiz because of the similarity of the settlement with his hometown at Valdevieso, which was the seaport Cadiz in Seville, Spain.
In the year 1878, Cadiz became a municipality independent from Sarabia (now E.B. Magalona) with Antonio Cabahug as the first gobernadorcillo. Cabahug was said to have brought the first sugarcane cuttings that were planted on the soil of Cadiz.
At the onset of the American rule, Cadiz was on its way to prosperity with the coming of two lumber companies to the area. Unluckily, one burned down in 1921, while the jurisdiction of the other lumber company, which became famous was transferred to Sagay.
On May 5, 1967 an event took place in the shores of Cadiz. Three whales landed in its shores.Each measuring forty feet long and eight feet in height, these mammals were said to have lost its course and found themselves in Cadiz shores. On May 10 of the same year, another group of nine was seen on the bay. Due to this incident Cadiz is identified today as the city of whales.
On July 4, 1967, Cadiz was inaugurated as a City with the approval of Republic Act 4894 in June 17, 1967 in Congress. The said Act was authored by then Congressman Armando C. Gustilo.