Question

What was helium used for in the past?

Answer 1

Helium used to be used in hot air balloons.  Then, when the Hindenburg exploded, annexed file, they realized that hydrogen was not only lighter, but it also was less flammable.  

Answer 2

Hot air balloons. They have a little hot plate/fire or whatever and they used, and that made the helium rise, thus rising the balloon.