The first true Star Trek convention was held in New York beginning on Friday,
January 21, 1972 and ran through the 23rd. It was started by a small group
that collected enough money, and rented a hotel room ballroom, attracting a
group of like-minded fans,

James Doohan (“Scotty”) speaking to the crowd at an early Star Trek convention.

Leonard Nimoy speaking at the 2011 convention