In the United States, the most-populous cities, such as New York City, Philadelphia, Boston, and Chicago initially implemented dial service with telephone numbers consisting of three letters and four digits ("3L-4N") according to a system developed by W. G. Blauvelt of AT&T in 1917. This system mapped the letter of the telephone number to the digits on the telephone dial. In 1930, New York City converted to a 2L-5N plan. Most other major Canadian and US cities, such as Toronto and Atlanta, were converted from manual exchanges using four digits to a local 2L-4N numbering plan. For example, in Montréal, "ATwater 1234" was dialed as six pulls on the dial ("AT1234") to send the digit sequence "281234". Eventually, starting in the late 1940s, all local numbering plans were changed to the 2L-5N system to prepare for nationwide Direct Distance Dialing. For example, under this system, a well-known number in New York City was listed as PEnnsylvania 6-5000.