Here's that link:

http://www.john-jacob-niles.com/gambling_songs.htm

There's quite a bit of information on that page. It starts with

The Gambling Songs were written by my father, John Jacob Niles, at the request of the famous baritone John Charles Thomas. John Charles Thomas, who had a very distinguished Metropolitan Opera Company of New York, became very well known with the American public on the radio. His renditions of "Annie Laurie" or "On the Road to Mandalay" were very popular with the radio audiences.

It goes on to talk about how the two worked together on some songs for Mr. Thomas, and other Niles side stories. An interesting read.