Anyone Speak Polish? And Know the Significance of This Poster?

The below poster from 1958 is for sale on EBay.com. The owner doesn’t know its significance other than it mentions “West Conshohocken” on the bottom right. Anyone know Polish or what happened in 1958?

If you want to zoom in on a specific section, go to the link to EBay.com above.

West Conshohocken Polish