Site Selection for the 1974 Worldcon was conducted by L.A.con I, the 1972 Worldcon. The bidders were New York in '74 and DC in '74. At the last minute, New York in '74 withdrew and DC in '74 was declared the unanimous winner and went on to run Discon II.
There were 109 mail ballots, 147 at-con ballots for a total of 256 ballots. No voting breakdowns were released.