On Wednesday, October 4, 2000 at 12:00:00 AM UTC-7, John H. Campbell wrote:
Interesting challenge. No direct counter-claims, but some related thoughts:

1) I thought that the Toledo Glider Club was active ca 1929 via Ed Knight
and the Funk brothers, contemporaneously with other nearby groups like the
Akron Glider Club, Gliders, Inc., etc.

2) Maybe "forwards" is the way to search. For instance, E. W. Teale's "The
Book of Gliders": (pub. 1930) had a list of American glider clubs. Which of
these are still in existence today, if any--with a continuous lineage?

3) Many American colleges have a history of glider clubs going way back,
although "continuous existence" is awful hard to come by for a campus
student group. For example, the University of Michigan at Ann Arbor had
official student-organization clubs (re)started in 1984, 1951, 1933, 1928,
and 1911. The Cornell Glider Club first appeared in Ithaca in 1909. The
world's first "glider contest" was Memorial weekend 1911, hosted by Harvard,
attended by MIT, Tufts, Cornell and many more, sanctioned by the
Intercollegiate Aeronautical Association out of U. Penn.

John H. Campbell
Collegiate Soaring Association
www.win.net/~greeley/coll/home.htm

The historic Southern California Soaring Association, was responsible for some of the Sierra wave project. I am not sure just how long it's existence goes back, certainly well before the war. The famous "Exploring the Monster" publication has some details about these pioneers.
Although they merged with the Douglas Soaring Club about fifteen years ago, now the new name is The Southern California Douglas Soaring Association.
Sadly this club now is going through a merger once again due to inactivity.