There is a granite gross erected on a peninsula in the small town of Trinidad, California. Picture of it here. It reads:
“Carolus III Dei G. Hyspaniarum Rex”
which is apparently “Charles III, King of Spain”
But what does the “Dei G.” part mean?
If it helps, the context is that the original cross was erected by early European explorers, then replaced with a more permanent cross in 1913 when the old wood one rotted away.
Hmm… does it mean “Dei gratia”, “of grace” or “by the grace of God”? If so, what is the meaning of that phrase in historical royal contexts?
Compare this to:
Her Majesty Elizabeth the Second, by the Grace of God of the United Kingdom of Great Britain and Northern Ireland, and of Her other Realms and Territories Queen, Head of the Commonwealth, Defender of the Faith.
In Latin: Elizabeth II, Dei Gratia Britanniarum …
Thank you all 
Note that Spain is pluralized: King of “the Spains”. The plural refers both to the Roman provinces into which the Iberian Peninsula was divided and to his being lord of several Spanish realms.
Interesting. This is for a project we’re working on for kids, so I’ll probably leave out that little bit of detail, but it’s interesting nonetheless!
Why were these “Spanish realms” instead of just parts of Spain?
For a long time the Iberian peninsula was divided into a (variable) number of kingdoms - Navarre, Asturias, Aragon, Castile - most of which had variable borders. Spain was a cultural concept rather than a political one. At various times different kingdoms were connected by marriages between their royal families, whicn in time would mean that different kingdoms were ruled by relatives - sometimes close relatives.
In the fifteenth century the Kingdoms of Castile and Aragon were (in practice, if not formally) united by the marriage of their respective monarchs, Isabella and Ferdinand, and towards the end of the century they jointly conquered the Kingdom of Granada. The effectively united most of what is now Spain. Their descendants were Kings of Castile and Aragon (and often other places as well); they were often referred to as Kings of Spain, although they didn;t formally claim that title.
For example, in a Treat of 1604 the then King style of “Philip the Third, by the grace of God, king of Castile, Leon, Aragon and the Two Sicilies, Jerusalem, Portugal, Navarre, Granada, Toledo, Valencia, Galicia, the Majorcas, Seville, Cordoba, Corsica, Murcia, Guinea, Algarve, Gibraltar, the Canary Islands, also of the Eastern and Western Indies, and the islands and terra firma of the Ocean Sea, archduke of Austria, duke of Burgundy and Milan, count of Habsburg, Barcelona, and Biscay, and lord of Molina, etc.” in full and “Philip III, King of the Spains” for short.
Thank you, UDS, for that detailed explanation! I never knew there was so much complexity to their history.
And UDS left out Portugal, which would also be part of the latin Hispania, and which started life under that name as a condado of León, but which evidently isn’t part of current Spain. The only man who can claim to have been king of all of Hispania after the Moorish invasion is Philip II. The Muslim parts were as messily entertaining, specially during the taifas period (the Caliphate of Cordoba disintegrated into tiny kingdoms called taifas).
There’s a TV series on Isabel (I of Castille) currently running on Spanish TV; I haven’t watched it, but I can tell you the family relations alone are enough to make those in Game of Thrones easy to follow. The Houses of Trastamara didn’t last long under that name, but in the short time they were around they were everywhere.
Compare ARS GRATIA ARTIS.
Note that this situation of a bunch of kingdoms being united into one was far from unique to Spain. Germany and Italy have also, for most of their history, been loose conglomerations of many independent or semi-independent realms.
And the UK. It was in a thread about the UK that I learned the name for “several realms which share the same head but which are not the same political entity”: personal union.
The UK isn’t quite the same, since it’s only three-and-a-fraction realms, not nearly as many as Spain, Italy, or Germany had, and the realms of the UK still have a larger degree of separateness than those other European countries now have.
But the concept still works, and teaching it or not is one of the big levers of centralist, regionalist and independentist politics here.
Aragon was a personal union for centuries; Aragon, Castille and Navarre were in personal union from 1516 (accesion of not-yet-Emperor Charles to the thrones of Aragon and Navarre and to guardianship of Castille) to 1715 (end of the War of Succesion and absorption of the Crown of Aragon into Castille); Castille and Navarre remained in personal union until 1841 (signature of the Treaty of Sisterly Union as we call it, Tratado de Hermandad, or Agreed Law as the Castillians do, Ley Paccionada). But not once was that mentioned in my classes: “Spain was united in 1492 with the conquest of Granada”. United? Not even in personal union at that time!