Older cars had a small vent hole in the filler cap. After that, they had a vent pipe that vented underneath the back of the car. They then went to a vent pipe from the tank (or filler neck) cannister in the engine bay to absorb the vent gasses, which is then purged into the intake system when the car is started. I think they introduced the cannister system about the time cats became standard, so around 1993.