mission · 301 · Vagharshapat
Tradition sets it at 301: Gregory the Illuminator, freed from the pit of Khor Virap, healed and baptized king Trdat III, and Armenia became the first kingdom to make Christianity its established faith — a generation before Constantine's conversion, and the root of the Armenian Apostolic line in this dataset.
Armenia the first kingdom to establish Christianity — its catholicate has run from Gregory's line to this day.