<P> Interchangeable NPA codes are introduced in Washington and Alabama, and some 40 new area codes are introduced through the year 1999 as pent - up demand for code relief is implemented . This includes two additional toll - free prefixes as the 888 code was quickly exhausted by assorted wasteful practices). Since 1999, a more steady rate of area code introductions has taken place, the rate being slower due to one or more factors: * economic recession, * consumer resistance, * conservation measures or regulatory measures, * pent - up demand being satisfied, * new market entrants leaving the business . </P> <P> With overlays in several areas (the relief method of choice in Canada since 2000), ten - digit local numbers are now supplanting seven - digit dialing; as of 2019, only three Canadian area codes (506, 807 and 867) will still be single - code areas (no overlay) and allow seven - digit local dialing . Although fewer American area codes are overlaid, seven - digit dialing is also disappearing in the United States . </P>

When did telephone numbers change to 7 digits