519 is the telephone area code which covers most of southwestern Ontario and was introduced in 1953 from portions of area codes 416 and 613. In 1957, parts of 519 and 613 formed 705. It is mostly bounded by area code 905, except for Simcoe County which is bordered by 705. It was overlaid with the new area code 226 on October 21, 2006, at which time ten-digit dialling became mandatory. Area code 226 is Canada's 25th geographical area code (not including area code 600).