1969 Grid lines added to map to aid in locating cities listed in the index. Press run reaches 2,000,000 copies. 1971 Indian reservations shown for the first time. Begins showing locations of hospitals providing 24-hour emergency service. First map to show Amtrak rail lines.
Department publishes first mass transit map.
Frequency changes from annual to biennial to cut costs. Begins showing exit numbers along freeways. 1978 Seaports shown for first time. 1980 Press run reaches 3,000,000 copies. 1992 Sites of underwater preserves shown for first time.