Quốc ngữ — literally "national script" — was not Alexandre de Rhodes's invention alone. Earlier Portuguese Jesuit missionaries had begun adapting the Roman alphabet to Vietnamese phonology in the early 17th century, and de Rhodes built on their work. But his 1651 catechism was the first substantial printed document in the system, and its printing in Rome gave the script an official, circulated form. For two centuries it remained primarily a missionary tool. Only in the late 19th and early 20th centuries, under French colonial administration, did quốc ngữ displace Chinese characters as the standard writing system for Vietnamese. The script that de Rhodes worked out in a village in Phú Yên now appears on every street sign, newspaper, and phone screen in Vietnam.

Mằng Lăng is also where Andrew — Anrê Phú Yên — was born, around 1625. He was baptized young and became a catechist under de Rhodes. When he was arrested by Vietnamese authorities in 1644, he was barely nineteen years old. He was executed — beheaded, with his heart removed and displayed as a warning — for refusing to renounce his faith. The account of his death, preserved in missionary records, describes him dying with prayers on his lips. He was beatified by Pope John Paul II on March 5, 2000, and is venerated as a patron model for Vietnamese Catholic youth. The courtyard of Mằng Lăng Church contains a man-made hill with stone carvings depicting his life and death, and the underground bunker beneath it preserves both his story and the de Rhodes catechism.

The present church building dates to 1892, constructed under French missionary Father Joseph de La Cassagne — known locally as Cố Xuân — who served as the first parish priest. It is Gothic in style: pointed arches, two bell towers flanking a central cross, ornate patterned surfaces. The exterior is a grayish-green that absorbs the tropical light differently than European stone would, softening the hard northern European forms into something that fits the surrounding landscape. The building covers more than 5,000 square meters of ground. Mằng Lăng translates to a tree that once grew here, now largely gone from the area, its name surviving in the place that outlasted it.

The historical roots of this site run deeper than Christianity. Vietnamese border settlements in Phú Yên were documented as early as 1475 during the Lê dynasty, meaning this region was already being incorporated into the Vietnamese state four centuries before the church was built. Early Christian activity came quickly: Princess Ngọc Liên, baptized as Maria Mađalêna in 1636, established a chapel in the area just a few years before Andrew's death. The encounter between Vietnamese political expansion, Cham cultural precedents, and Catholic missionary presence produced something unusual here — a place where a new way of writing a language, a martyr's story, and a church architecture all converged, and where a glass case in an underground bunker preserves the earliest trace of the written Vietnamese most people now use without thinking about its origin.