An Emergency Medical Hologram Mark I was the first type of Emergency Medical Hologram invented by Dr. Lewis Zimmerman in 2371.
In 2369, Dr. Zimmerman produced the first working prototype of his invention and presented it to Starfleet Command, who accepted it to use on Starfleet ships. Dr. Zimmerman, proud at his achievement, decided to program the EMH Mark I with both his physical and psychological likeness. The resulting hologram was arrogant and irritable, and as a result was poorly received by many Starfleet doctors. This resulted in nicknames like "Emergency Medical Hotheads" and "Extremely Marginal Housecalls". Some biological Starfleet doctors even went so far as to object to the use of the EMH. Doctor Beverly Crusher swore that she would never use one, although she was forced to do so in order to create a distraction while the Borg tried to assimilate the USS Enterprise-E, allowing her, her medical staff, and her patients, notably Lily Sloane, to escape from sickbay.
The EMH Mark I was first activated in 2371, and was programmed with 5 million possible treatments from the collective information of 2000 medical references and the experience of 47 individual medical officers. The EMH was also supplemented with contingency programs and adaptive programs to learn while serving as a supplement of a normal medical staff in cases of emergency. It contains 50 million gigaquads of computer memory, which is "considerably more than most highly developed humanoid brains.
Eventually it was concluded that the EMH Mark I was defective, and they were bounced out of the medical corps. While an ashamed Dr. Zimmerman tried to have them decommissioned, Starfleet reassigned them to scrub plasma conduits on waste transfer barges. Later the Mark I's were also deployed in other menial tasks, like dilithium mining.
Of at least 678 Mark I's created, 675 were reassigned, but at least some escaped by virtue of their ship being lost in the Delta Quadrant; one aboard Voyager, one aboard the Equinox, and the backup copy of Voyager's EMH which was in the possession of the Kyrians – assuming these were not counted among those reconfigured.
By 2377, the Mark I programs were reconfigured to work at a Federation mining colony in replacement of other forms of labor. These programs, having been resigned to their new function, were able to obtain bootlegged copies of the holonovel Photons Be Free and view them. One of the EMH miners found the holonovel "provocative".
However, later that year, programmers found the error in the EMH's program that caused it to be irratable and annoying, and fixed the error, allowing the EMH Mark I's to go back to regular service as EMH's on Starfleet ships. By 2377 the Mark II had been replaced by a Mark III, followed by a Mark IV.