This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
Europe gathers forty five nations running from a city state defined by one church to a country that converted its whole population by a single legal vote.
Four states still establish Catholicism where most of the continent disestablished it. Vatican City is the extreme case, a state with no population beyond clergy and guards, existing to govern the worldwide church through the Holy See. San Marino, Monaco and Liechtenstein each keep a constitutional link to Rome their larger neighbors dropped: Monaco's constitution names Catholicism the religion of the state outright, and San Marino traces its founding to a Christian stonemason fleeing persecution in the year 301.
Orthodoxy carries national identity elsewhere the way Catholicism carries it in the microstates. Russia's church, adopted from Byzantium in 988, survived Soviet suppression and rebuilt ties to the state; Greece's constitutionally recognized church stands over Mount Athos, a monastic republic closed to women for a thousand years; and Serbia's oldest monasteries, standing today in Kosovo, carry the church's memory of the 1389 battle Serbs still narrate through liturgy and epic poetry. Bosnia and Herzegovina shows what happens when three such traditions meet as equals, Bosniak, Serb and Croat doubling as religious and national labels at once.
Two Nordic countries chose the opposite of imposed uniformity. Iceland converted at law around the year 1000 rather than by war, which is why its scribes preserved the Norse material instead of burning it, and Sweden disestablished its Lutheran church only in 2000. France's laicite, splitting church from state in 1905, sits at the same secular end despite its Catholic architecture, while Germany still carries the line the Reformation drew at Wittenberg in 1517.