Hi, Seamus -
Here's a quote from The Book of World-Famous Music (James J. Fuld, 1966, 1971):

music and words by Thomas P. Westendorf. The first printing of this song was in Church's Musical Visitor (Supplement), Cincinnati, March, 1876.
The history of this song has been ably written by Richard S. Hill in "Getting Kathleen Home Again." The song is at times mistaken as an Irish ballad. That it was written in Kentucky to cheer up a homesick wife who wanted to return East is shown by Hill to be unlikely. Westendorf, a musician and composer, was born in Bowling Green, Caroline County, Va., in 1848 and died in Chicago in 1923.

-Joe Offer-