As far as I know this song was written about 1975 by a singer/songwriter in old Town who was also an engineer on the EVANSTON EXPRESS CTA train line (Chicago Transit Authority) -- an elevated train affectionately called "the L" in Chicagoland and environs. Evanston is the first suburb north of Chicago on Lake Michigan. Just North of Evenston in the suburb called Wilmette (where George and Gerry armstrong lived for so many years).

When the train got to the end of the Evanston line, he always used to shout out their location. Therefore the first verse of the song:

"Wilmette, Wilmette, Wilmette", he cried,
"Wilmette, Wilmette", cried he,
"I've just returned from the salt, salt sea,
And it's all for the love of thee."

(In Chicago we were always certain thiat this actually referred to Lake Michican which looked like an ocean because you could not see the other side of it.

;-) Art Thieme