Designing the timeline
Two thousand years of European crowns, on one timeline
I wanted to see which monarchies existed at the same time. That simple question turned into a problem about names, borders, family trees and the misleading confidence of a beautiful diagram.
Most histories of monarchy arrive one country at a time. You learn the Tudors, then perhaps the Bourbons, the Habsburgs or the Romanovs. Each line makes sense on its own. What disappears is simultaneity.
Henry VIII and Francis I were near-contemporaries. Charles ruled the Spanish crowns jointly with his mother Joanna before adding the imperial office to his other titles. James VI of Scotland could become James I of England without Scotland and England becoming the same country. Those are easy facts to recite and surprisingly hard facts to hold in your head at once.
The project began as six coloured bars. Rome, Byzantium, England, France, the Holy Roman Empire and Castile. It proved that a shared time axis was useful, but little else. Every bar looked independent. There was no way to show that a single person held several crowns, that two kingdoms shared a monarch, or that one political phase ended by becoming part of another.
The temptation of the river
A Sankey diagram looked like the obvious next step. Monarchies could become streams. They could split, curve and merge. The result would resemble one of those long historical charts where civilizations flow down the page. John B. Sparks's 1931 Histomap is still compelling for exactly that reason.
It would also lie.
A Sankey needs a quantity. A thick line means more energy, money, material or people passed through it. What would the thickness of France mean here? Territory? Population? Revenue? Military power? Those measures exist for some periods and collapse into guesswork for others. If line width carried no value, the chart would borrow the authority of a quantitative form without doing the accounting.
So every monarchy in this timeline has the same height. Duration is the only continuous measurement. The visual can say that the Byzantine Empire lasted longer than the Kingdom of Italy. It does not pretend that Byzantium was six times more powerful.
A family tree was no better
The second idea was a dendrogram. Monarchies are dynastic, after all. Put the houses in a tree and let the branches explain the crowns.
That works until the first marriage, election, restoration or disputed succession. A person has two parents. A royal house has cadet branches. An elective crown can move between families. The same monarch can hold several titles, and a personal union can end without either state ending. Europe does not give you a tree. It gives you a graph with a habit of tying itself in knots.
The final design keeps a timeline as its spine. Political phases are bars. Houses are narrower bands inside them. Selected reigns are dots with short duration lines. Typed connectors do the work that a family tree or Sankey would otherwise blur together.
Five dates that explain the chart
843: an empire becomes a set of arguments
The Treaty of Verdun divided the Carolingian Empire among the sons of Louis the Pious. It did not manufacture France and Germany in their modern form. It did produce western, middle and eastern political lines that later rulers kept reusing.
On the chart, Francia ends in 843. A partition connector points toward France and toward the precursor story of the Holy Roman Empire. The line is an interpretation, so the detail panel says exactly what it means.
1066: a house changes, a kingdom does not
William's conquest of England is a useful example of why house and polity need separate records. The Kingdom of England continues, while Harold II's short Godwin reign and the Norman conquest change the ruling dynasty within 1066. At annual scale those transitions occupy almost the same point, but the English phase bar does not restart.
1519: Charles V breaks the one-person, one-country model
This is the date I keep coming back to. Charles began ruling the Spanish crowns jointly with his mother Joanna in 1516 and was elected King of the Romans in 1519; papal coronation as emperor followed in 1530. He did not fuse the Spanish kingdoms and the Holy Roman Empire into one ordinary state. He was one person with several titles and jurisdictions.
The data therefore has one Charles V and separate reign records. Move the year line to 1519 and his name appears in more than one lane. That is a small database decision with a large visual payoff.
1707: sharing a monarch is not the same as sharing a state
James VI of Scotland inherited the English crown in 1603. The two kingdoms shared a sovereign for more than a century while keeping separate parliaments. In 1707 the Acts of Union created Great Britain.
Those two relationships need different marks. The first is a dashed personal-union connector. The second is a state-union connector that ends the English and Scottish lanes and begins the Great Britain lane.
1918: several long lines stop together
The end of the First World War is where the continental comparison earns its space. The German and Austro-Hungarian monarchies ended in the same narrow slice of time. The Russian monarchy had fallen the year before. The Ottoman sultanate survived until 1922.
A national timeline shows one collapse. The shared axis shows a political system coming apart across the continent.
Modern countries make poor containers for medieval history
There is no honest way to draw this using today's countries as permanent rows. "Germany" before 1871 would swallow the Holy Roman Empire, Prussia, Austria, Bohemia and dozens of states that did not think of themselves as administrative pieces of a future nation. "Italy" would do the same to Savoy, Sardinia, Sicily, the Papal States and the northern republics.
The timeline uses historical polities instead. Some are composite. Some overlap. England, Great Britain and the United Kingdom get separate lanes because their constitutional identities differ. Spain overlaps Castile and Aragon during the dynastic period because a shared monarchy did not immediately erase either crown.
This makes the chart messier than a classroom poster. Good. The mess is part of the subject.
The dates need footnotes
The western imperial tradition later identified with the Holy Roman Empire can be traced to Charlemagne's coronation in 800, while the continuous imperial line used here begins with Otto I in 962. France can be traced from West Francia in 843 or from Hugh Capet's accession in 987. The Roman Empire did not experience 395 as a modern corporate split.
I chose dates that make the cross-European comparison legible, then recorded the alternatives in notes and events. Charlemagne's coronation remains visible even though the continuous Holy Roman lane begins with Otto. France begins with West Francia, but the Capetian band starts later. The chart does not eliminate the disagreement. It gives the disagreement somewhere to live.
A chart for browsing, not a final answer
The current dataset has forty-eight polity lanes, 197 selected reign records and forty typed relationships. It includes every surviving European monarchy and a broad set of former kingdoms and empires. It still leaves things out. The German and Italian states alone could fill another project. So could royal genealogy, colonial titles or the elected kings of the Commonwealth.
The overview is meant to produce questions. Why does this lane stop? Why does that house appear in three countries? Who else was ruling in 1519? Each selected mark opens a short explanation and its references. The methodology page records the scope and the known compromises.
I started by wanting one big timeline. What I ended up needing was a timeline that admits where the lines are uncertain.