The Mexico (Mo.) Ledger published this brief article about the changes in phone numbers in Centralia, Sturgeon, and Clark a little more than a week before the changes were to take effect on December 19, 1971. The article was published December 11.
The headline, EMpire and SKyline Out; Try Dialing MU After 19th, was a reference to the original named prefixes for the three exchanges. By 1971, though, the use of named prefixes had been phased out in favor of all-numeric phone numbers. Still, the article warned that "recalling the old EMpire-2 and SKyline-7 begining for Centralia and Sturgeon won't help dialers", instead suggesting that callers use "MU", for the University of Missouri in Columbia, as a way of remembering the new 682 and 687 prefixes.
The article, datelined Centralia, also reported the shift of Sturgeon and Clark from the 816 are code to the 314 area code. It also pointed out that the changes also enabled the use of direct-dialed long distance calls in the three communities.
As for the reason behind the changes, the article quoted R.T. Willis, service supervisor for General Telephone, as saying the changes would "permit proper functioning of new central office equipment", without further elaboration.