Google Books
The History of the Telephone
By Herbert Newton Casson
Chicago, IL: A. C. McClurg & Co.
1910
Pg. 271:
China, Japan, and France have sent delegations to New York City -- "the Mecca of telephone men," to learn the art of telephony in its highest development.
11 July 1913, New York (NY) Times, pg. 11 ad:
"New York is the
Mecca of Telephone Men."
(...)
New York Telephone Company