Each day, Benzinga will take a look back at a notable market-related moment that happened on this date. What Happened? On Dec. 20, 1966, the New York Stock Exchange switched to a fully automated computerized trading system for the first time. Where Was the Market? The S&P 500 was trading at 80.96 and the Dow Jones Industrial Average was trading at 794.59. What Else Was Going On in the World? In 1966, Mississippi became the last state in the U.S. to repeal a statewide prohibition on alcoholic beverages 33 years after federal prohibition had been repealed. A dozen eggs cost 60 cents. The Digital Era Most investors probably think of the late 1990s and the beginning of the internet era as the period when computers really got their hooks into Wall Street. In reality, trading at the NYSE has been computerized going all the way back to 1966. The first …