The earliest Careaga of written record was a Spanish nobleman born in medieval Castile and sent to Mexico as a military man by the King of Spain. A descendant of his, Colonel Satornino Careaga, was the first of the family to travel to Monterey, California. He was a member of Captain Muñoz's command who risked his life and suffered great pains to protect an exposed and seemingly doomed San Jose Mission. He was survived by two sons, Ramon F. Careaga and Juan B. Careaga. Along with a mutual friend, Daniel Harris, the brothers bought approximately of land formerly belonging to the De la Guerra family (early Spaniards who figured prominently in the state history). Later, in the division, Harris took some while the Careaga brothers held more than 10,000. It was on Ramon Careaga's land that oil was first discovered in the Santa Maria Valley.
The alternate spelling of the esteemed surname is "Kareaga." It is derived from the spanish "kare" (lime) and "aga" (place), thus seems to refer to a "limy place." Several medieval estates of the family's continue to exist in Spain today, including two located in Markina-Xemein and Murelaga. The family coat of arms is distinguishable by its gold and silver tones as well as two wolves of saber.