Neither state ever designated itself as "North Yemen" and the term only came into general use when the Federation of South Arabia gained independence as the People's Republic of South Yemen in 1967 making such a distinction necessary. Prior to 1967, the North was known in short form simply as "Yemen." In 1970, South Yemen changed its name to the People's Democratic Republic of Yemen thus eliminating any directional reference in either of the Yemens' official names but the existence of two Yemens preserved the North Yemen and South Yemen designations in popular parlance. Alternate forms were "Yemen (Sanaa)" for North Yemen and "Yemen (Aden)" for South Yemen after their respective capital cities.
The merger of the two Yemens in 1990 ended the term's association with an independent state but "North Yemen" continues to be used to refer to the area of the former Yemen Arab Republic and its history and, anachronistically, to pre-1967 polities and events (e.g. the Mutawakkilite Kingdom of Yemen or the North Yemen Civil War).
Area: 167,943 km² (64,843.15 sq mi)
Population (1990 estimate): 7,160,981
Population density (1990 estimate): 42.6 /km² (110.4 /sq mi)