after graduation, ludewig worked at the amsterdam office of architect p.j.h. cuypers, probably as a draftsman. in 1902 he began his own office in arnhem and moved two years later to nijmegen. he built several houses, reconstructed wijchen castle and restored churches in beek, leur and rosmalen. in 1912 he migrated to the united states, hoping to find opportunities to design churches. he set up an architectural office in st. louis, missouri and later moved to holland, michigan. in the nineteen years of his american career, ludewig built 21 churches and chapels, 11 schools and 10 presbyteries. his most important work, and one of his last, was the pontifical college josephinum in columbus, ohio. ludewig retired at the age of 69 and, after suffering from heart ailment for 18 months, died in grand rapids, michigan in 1940. his grave is at the pilgrim home cemetery, holland, michigan.