For me, it was 1959, I was five years old, and my mother took me to a downtown Indianapolis theatre to see North By Northwest and Gordon Scott in Tarzan's Greatest Adventure.
I haven't ever gotten around to watching NBN again, but I can still remember certain scenes from it. Oddly, probably the most famous scene from that movie, where Cary Grant is being chased by a crop-dusting plane, I don't remember. Certain scenes from the Tarzan film - one of the all-time best, btw - stuck in my long-term memory, as well.