The Mars maps on this site are based on data mostly from the Viking 1 and Viking 2 missions which orbited Mars, collecting data from 1976 to 1980.
 

Mission	Encounter date(s)	Type of encounter	Significant discoveries	Closest approach	Best resolution	# of pictures	Percent of planet mapped
Mariner 4	15 July 1965	flyby	densely cratered terrain	9846 km	~ 1km	21	1%
Mariner 6/7	31 July 1969  5 August 1969	flyby flyby	Olympus Mons eroded features	3431 km 3430 km	300 m  300 m	75 124	10%
Mariner 9	13 November 1971 to 27 October 1972  (operational in orbit for 349 days)	orbiter	fluvial channels huge volcanoes mapped 100% of planet Valles Marineris layered polar terrain dust storm observastions past geologic activity first closeups of Phobos & Deimos	1250 km	50 m	6786 of Mars	100%  at 1-3 km res.
Viking 1	19 June 1976 to 17 August 1980 (orbiter)	orbiter and lander	high resolution images surface chemistry information atmospheric chemistry biologic tests	300 km	8m, 150 m lander: ~3 mm	>33,000 (some color)	100%
Viking 2	7 August 1976 to 25 July 1978 (orbiter)	orbiter and lander	see Viking 1	300 km	8m, 150 m lander: ~3 mm	~16,000 (some color)	100%
Mars Global Surveyor	12 September 1997  to present	orbiter	spectral mapping ancient hydrothermal activity  localized magnetic regions mapped duststorm evolution data is still being analyzed...	258 km	1.4 m	still obtaining images	still obtaining images
Mars Odyssey	24 October 2001 to present	orbiter	data gathering in progress	still obtaining data	still obtaining data	still obtaining images	still obtaining images