What makes these directories so helpful? The directories, usually published annually, provides a listing of every Catholic-run church, hospital, school, college, orphanage, asylum, convent, seminary, and missionary in the United States. And, actually, many of the directories that include the U.S. also include British North America as well. This one, from 1876, includes a listing of clergy from Ireland, too:
The directories also have an obituary section in which the deaths of priests and other female and male religious members that occurred over the past year are listed. Typically, due to space constraints, not much information is listed: Date, name, location, age, order - SOMETIMES place of birth and cause of death are listed, but not always. The bonus in the obituaries is that women religious often have their birth names listed next to their religious names and titles.
Even if you do not have ancestors who were priests or other Catholic religious members, you may find these directories helpful. Perhaps you know your relatives were Catholic and you know the town in which they settled. Use these directories to figure out what church they attended (and then try to track down those sacrament records!). Perhaps you don't know where your Polish Catholic immigrant great-grandparents attended church in a bigger city, like Cleveland. Use these directories to figure out where the Polish Catholic churches were located and start researching those churches first. Remember that Catholic churches and schools are not static entities; new ones open, old ones close and merge with other parishes. These directories give us a snapshot of which parishes and schools were open and active every year in just about every location in the country.
I was pleasantly surprised to see how many Catholic directories from the 19th and early 20th centuries can be viewed and downloaded for free through Google Books. Simply go to Google Books and type "catholic directories" in the search box. You will be able to browse through them and, if you are looking for a specific year or range of years, you can narrow down your search even further.