From
http://www.nytimes.com/2012/01/22/books/review/guidebooks-to-babylon.html?_r=1&ref=prostitution&pagewanted=all
And even the drabbest directories may still serve a useful purpose. Gilfoyle used them to help map Manhattan’s 19th-century brothels as they moved up and down the island, from Five Points to the Tenderloin, like a persistent rash. Others have an archaeological value of sorts. In Kansas City, I recently used the “Little Black Book” to tour the forgotten red-light district that once lay by the Missouri River, now overshadowed by an Interstate highway.
In the 21st century, the genre is enjoying a revival in the many Web sites devoted to prostitution, where Yelp-style reviews are becoming longer and more detailed. The form could not seem more ephemeral. But perhaps the authors of these jottings should pause to tweak their Rabelaisian prose and keep one eye on posterity. Who knows what historian in the distant future will pore over their words, imagining our era’s wicked ways?