Re: More than you ever wanted to know about North American Telephone Exchanges

The whole kit and kaboodle can be found at the below url. In the meantime, did you ever think you'd get an etymology for "555?"

"It was considered difficult to form words/names easy to pronounce from the letters JKL, PRS, WXY. However, San Francisco had their KLondike exchange (55x), and in the later 1950's and early 1960's, fictitious exchange namesin radio/TV/print entertainment and advertisements used KL-5 or KLondike-5."

http://hyperarchive.lcs.mit.edu/telecom-archives/archives/history/exchange.names.recommended