DCHP-1 Online
permafrost line North 
the line marking the southern boundary of permafrost.
- 1957 It is only an accident of geography that the 1,670-mile-long Alaska Highway rarely broached the permafrost line or it might not have been finished by November 1942.
- 1965 The "permafrost line" runs in a very irregular line from the Ontario shore of Hudson Bay northwestward, passing north of Reindeer Lake and Lake Athabasca and along the north shore of Great Slave Lake.
- 1957 It is only an accident of geography that the 1,670-mile-long Alaska Highway rarely broached the permafrost line or it might not have been finished by November 1942.