string splitting

[rdharles at gmail.com]

Hello,
I have thousands of files that look something like this:

wisconsin_state.txt
french_guiana_district.txt
central_african_republic_province.txt

I need to extract the string between the *last* underscore and the
extention.
So based on the files above, I want returned:
state
district
province

My plan was to use .split or .find but I can't figure out how locate
only the last underscore in the filename.

Anyone have any ideas?

Thanks.
R.D.