But from McNamara's Blog comes this interesting factoid:
For most of the 1800's, Catholic priests in the United States actually wore suits and ties were addressed as "Mister" rather than "Father." This was a holdover from the English Catholic tradition, where "Roman" clergy tried to make themselves as inconspicuous as possible in an anti-Catholic climate.
Things weren't much better in mid-19th century America. Even women religious weren't immune to this trend. When the Sisters of St. Joseph first came to Brooklyn in 1856, for example, they wore civilan garb lest they be attacked on the street by Nativists.
(Not long before, without provocation, a man walked up to a Sister of Charity in the streets of Boston, called her a "damned papist bitch," and slapped her face.)
In 1884, at the Third Plenary Council of Baltimore (which also gave us the Baltimore Catechism), clerical garb was mandated.