Correct. Welles broadcast it in '33 or '34 from a big station in NJ, and it scared the **** out of people at the time. That's not surprising as radio was the primary means that people got their information from - it would be like if CNN and Fox told everyone a week after 9/11 that they staged the whole thing.
The first movie version was in the mid '50s, and such it has a very strong anti-Communist subtext to it...but it's one of those cult classics that still holds value, a lot like "The Day the Earth Stood Still".