Second update from Tachoknight: Container is still an ammo can,
with some yellow paint. It's closer to the water than before (let's
see how water-tight these things can be!) but, ironically, in a
better spot, I think.
The major upside to the new location, and one of the reasons why I
chose it, was because of the beautiful view you get from the new
spot. Plus, you've walked all the way out here, what's a few more
feet, scrambling over rocks? 
.
First update from Tachoknight: The container is now an ammo can;
hopefully it will survive the winter weather better than the
previous container (which I found...most of it, anyway).
UPDATE (03/21/09): Placed a new cache at a slightly different
location. Coordinates changed, new hint added.
No matter if you come by car or public transportation, this
cache is the opposite of a drive-up. The terrain rating is for the
length of the walk in an urban setting. The park closes at
dusk.
Though the last 250 feet to the cache are definitely not
wheelchairs friendly at all, the rest of the way seems to be ideal
for wheelchairs and strollers. It would make a good cache for a
mixed group of disabled cachers and at least one who can manage the
final stretch through moderate vegetation and over rocks. So I
added the wheelchair symbol to the cache description for visitors
who scan for suitable caches by PQ. If anyone feels offended
because a successful hunt DOES require some assistance, please let
me know.
The park has changed a lot since my last visit in summer 2007.
Still, it remains an oasis of peace and remoteness right in the
heart of Chicago. And the views near the cache site are great both
north- and southwards.
Neighboring GCJNQ2 on your way has plenty of information about
the history of the peninsula. However, it's unsure if the cache
still exists. But most importantly, make sure to visit the
wonderful Little Travel Bug Hotel on the Prairie on your way.
The island seems to be closed during concerts at the pavilion.
If you plan to come during the evening, check out the concert schedule before your visit.