Does anyone know what kind of lilac bushes were around... oh.. say... 70 years ago in the western US?

We all know we're spoiled now with tons of variety to choose from, but way back when, they didn't have a nursery to go to, or mail order plants.

My mom has a big lilac bush that she grew from a sucker from her grandmothers lilac bush. I now have a sucker from my Mom's bush and am growing it!

Im mainly trying to identify the thing. No blooms yet (I hear it takes 3-5 years), but my Mom's blooms similar to the Blue Skies current day variety. Anyone know what was available then?