It's a tradition that has been around since her death. When Jesus was dying on the cross He consigned Mary to St. John's care, to take care of her. So, St. John, who was also the youngest of the Apostles, took her with him on his travels to spread the "good news." We don't know how long a time was involved but we do know that St. John traveled throughout Asia Minor and ended up all by himself...in Ephesus. Mary died there in her "simply stone house." THAT is all historical.
The history of Asia Minor is very complicated, as you can read on any site about its history. It seemed that the leaders and those people who lived there (from Jesus' time, through Constantinople to present day Istanbul) agreed to honor that particular site.
I always thought it odd that the Turks would honor "Mary's house," but they do. They, the Turks, don't maintain it, though, as they leave that up to Christians.
The last time I was there, a few decades ago, a contingent of U.S.A. Midwestern Catholics were the ones who maintained it.
There is a book you can buy called FOUR WITNESSES. It's editor is Rod Bennett, Ignatius Press. The authors are cited below.
It's about the "early Church in her own words." There are four authors, Clement of Rome, Ignatius of Antioch, Justin Martyr and Irenaeus of Lyons.
1. Clement of Rome and his Epistle to the Corinthians, was written about the same time as the Gospel of John. http://www.catholic.com/magazine/articles/did-john-write-his-gospel
2. Ignatius of Antioch was an early pastor of the Church at Antioch and was described by several ancient writers as "a hearer of the apostles." There are at least five certified epistles of Ignatius, all of them composed in or about 107 A.D.
3. Justin Martyr reported that the Church has spread across the known world by HIS times, the year 150 A.D.
4. Irenaeus of Lyons wrote a massive, five-volume work Against Heresies and recalls studying his theology at the feet of (St.) Polycarp. Polycarp was was personally taught by John the Beloved, who was personally taught by Jesus. All Catholic sites say that St. John was "the Beloved." Some of the other sites, non-Catholic Christian, cite a wide variety of opinions as to who "John the Beloved" was. There is no one agreed version for them.
I hope I gave you a decent answer. I still occasionally read the FOUR WITNESSES as I can read about Jesus from the words of men who witnessed those early Church fathers.
I appreciate the answer and references.
Oh; it's not so complicated.
1. Catholics formed at least 7 churches there.
2. They went belly up really quickly.
3. They were teaching error.
4. GOD was upset over them.
5. HE sent and angel to John so he could TRY to get their attention.
6. One can go visit the ruins of them today.