Originally known as Puerto de las Cabras (Port of the Goats), Puerto del Rosario was initially of little political importance on the island- living in the shadow of the previous capital of Betancuria. It had long been a fishing settlement and benefited from a sheltered natural harbour. The "Atlantic Navigator", written in 1854, describes the town then known as "Cabras" as "the principal port", but goes on to describe it as an "insignificant place". The "Atlantic Navigator" describes the makeshift landing area for shipping as "indifferent", while calling the "beach of shingles" where ships anchor as "still worse". Although the town was small and underpopulated, just 1,000 in 1936, all major exports and imports from the island were shipped from the harbour at Puerto del Rosario.
It was this status as the "principal port" of the island that saw it become the capital of the island in 1860. The port was popular for shipping goats, and this is where its original name came from. However, in 1957, it was decided that the name "Cabras" was not suitable. A more attractive name was selected and Cabras (goat) was replaced with Rosario (rosary).
During the 1960s there was rural to urban migration from the smaller villages and farm areas of the island into Puerto del Rosario. The population grew in these years. A further population growth occurred in 1976 when, due to the decolonisation of North Africa, the Spanish Foreign Legion made Puerto del Rosario their base.