International Meridian Conference
On 11 October 1883, a convention of railroad executives met in Chicago and agreed to the implementation of five time zones in North America, using as a basis Greenwich Mean Time. Before the invitations to the Washington conference were sent out on December 1, the joint efforts of Abbe, Fleming and William Frederick Allen, Secretary of the US railways' "General Time Convention" and Managing Editor of the "Travellers' Official Guide to the Railways", had brought the US railway companies to an agreement which led to standard railway time being introduced at noon on 18 November 1883 across the nation. Although this was not legally established until 1918, there was thus a strong sense of "fait accompli" that preceded the Washington conference, although setting local times was not part of the remit of the conference.
North American Numbering Plan expansion
The North American Numbering Plan was devised in the 1940s, implemented in 1947, and has provided customer direct-dialed long-distance telephone service since 1951. Occasionally, the growing demand for telephone numbers has mandated certain changes in the format of telephone numbers and method by which they are allocated to telephone companies. Instead of expanding the size of telephone numbers, as implemented in many countries outside North America, the NANP was designed as a closed numbering plan, having a fixed number of digits, three digits for the numbering plan area (NPA) code and seven digits for telephone numbers that are unique in each NPA. The telephone number was further distinguished as consisting of three digits that identified each central office and four digits for each subscriber station connected to the same central office. From 1947 to c. 1960, the initial two digits of the central office code were mapped to two letters of an often locally significant name, the central office name or exchange name. However, this scheme, practiced since its invention by W. G. Blauvelt of AT&T in 1917, prevented the use of numerous digit combinations that could only be associated with unpronounceable or, at best, confusable names. All-number calling removed these restrictions and permitted the phasing out of exchange names. Central office codes were initially still restricted from using digits "0" and "1" in the middle position, which provided a distinction to area codes, which always had "0" or "1" in the middle position. This last restriction was removed by 1995, with the phase-out of electromechanical switching systems by programmable electronic switching systems (ESS).