Back to the Massachusetts lake, as noted in the Wiki link, the locals refer to it as Webster Lake. Although there are several alternative spellings, this one shown at a shopping plaza near the site has 45 letters, add the word "Lake" and you're up to 49 letters:

A version was even put to music. If you want to learn how to say it, learn this song (lyrics included)!
http://youtu.be/yhL4rg7yO4EFrom a philatelic standpoint it's too bad they never had a post office, as it would have been a real challenge to get that name in the CDS on a postmark!