The final documents of the Inchon Synod give a brief history of evangelization in the diocese.The facts are not easy to find, but it is surmised that since Lee Seung-hoon (the first baptized Catholic ) and Whang Sa-yong (the writer of the Silk Letter) were active in the early Church, the gospel spread rather early in Inchon and Kangwha. And since there are many martyrs who were born, or at least resided in Inchon, we know that Catholics were living there during the persecution.
The Chemulpo parish, now the Tap Dong Cathedral parish, was the first parish of Inchon, established in 1889. With the Korea-France Treaty of 1886, missionaries were allowed to come to Korea and to Inchon to construct rectories and churches. With the increase of Catholics in October of 1958, Inchon became a separate deanery of the vicariate apostolic of Seoul, which was entrusted to the Maryknoll Fathers and Brothers. On June 6, 1961, Pope John XXIII made Inchon a vicariate apostolic, separating it from Seoul.
On March 10, 1962, all the vicariates became dioceses. Today there are no longer any foreign ordinaries, all is in the hands of the Korean Church. Inchon began its own diocesan major seminary to train seminarians for the diocesan priesthood, as well as to form future missioners for North Korea.
The Cathedral is considered a national treasure and there are plans with the city to set aside an area around the Cathedral for a park and exhibition hall. The present pastor of the Cathedral parish says: " Our Catholic community is like a giving tree; it unsparingly takes care of the parish, refreshes and gives rest to all those who participate, no matter how briefly. It also strengthens the faith life of our Christians, both by the beauty of the surroundings and by the example of our community life. We do not have many young people, which is a problem, but the Cathedral parish is trying to make the community a place of joy and peace for all."
