Part of the reason the What in the World cache has such large numbers is in it's early years, the owner allowed "armchair" logging, meaning you didn't have to actually visit the site to log the cache. You only had to explain to him what was at the location. Another reason is it is a very popular site, easy to get to, and a site which is attractive to many cachers.

That being said, I think the Fort Williams cache gets a lot of hits for a physical cache. I looked at a few other caches I thought were popular, but they don't have as many finds as Fort Williams. Perhaps one of our more southern cachers can think of a cache that gets hit more often?