Welcome to the forum.Second St John the Baptist Greek Catholic Church
was formed in 1900, by Ruthenian faithful of St John the Baptist Ukrainian Byzantine Catholic Church. There were approximately 1,900 parishioners at that time. It was the first Ruthenian congregation in Pittsburgh and was the mother church of Holy Ghost, Holy Spirit, and St John Chrysostom, all in Pittsburgh, and Holy Ghost in McKees Rocks.
Originally, the parish met in a rented storeroom at S 10th & Sarah Sts in Pittsburgh's South Side. The congregation relocated in 1901, to 613 E Carson St, Pittsburgh, where the parish was formally erected in 1901, under the patronage of St John the Baptist.
The temple was subsequently renamed as St John the Baptist Byzantine Greek-Catholic Church, possibly when it obtained its own building in 1901. However, I suspect that it was at some time afterwards. That you cite your grandparents as having been married at it in 1914 under that name suggests that you have seen documentation using that name in 1914 and lends credence to my suspicion. (John Schweich, our resident historian, may know more detail regarding that.) It was the home parish of Bishop Emil Mihalik, of blessed memory, first Eparch of Parma of the Ruthenians.
In 1958, the parish relocated to its present site, 1720 Jane St, Pittsburgh. The metrical books/sacramental records of the original parish are maintained at the present site. Contact information is here
As you note, some liturgical furnishings were moved from the original church to the new one, specifically the iconostasis (although it apparently required some reworking to fit) and a candle chandelier. There may have been others.
The parish has a cemetery on Connor Rd in Castle Shannon, PA, notable as the burial place of Andy Warhol, of blessed memory.
There is an exterior photo of the original temple in the Byzantine Slavonic Rite Catholic Diocese of Pittsburgh Silver Jubilee 1924-1949 Directory
. If you'd like a photocopy of that, pm your mailing address to me and I'll be happy to send it to you. I haven't yet been able to track down an interior photo.
Hope this info is of some help to you.