Great collection at the Art Institute in Chicago.
It was this scene of some old park with oddly dressed people enjoying themselves near the water. The colors were odd in that they seemed to be painted in dots.
Not long after, we had a field trip to downtown Chicago; I don't recall if it was a class or a family thing. A major part of the visit was to the Institute. There, I learned that the painting was Un dimanche après-midi à l'Île de la Grande Jatte by Georges Seurat, and I got to see it for my first time in all its glory.
Still later, during my college years in the 60's, I spent time in the windy city on various occasions and paid my second visit to the Institue. When I got to The Painting, and despite having seen it as a kid, I really wasn't prepared for its huge dimensions. The size is part of its impact of course.
I was also fascinated by the other impressionists, of which the Institute has, as you mentioned, an excellent collection.
Just a couple of Christmases ago during a visit with relatives in the area, I scheduled a day in downtown Chicago primarily to revisit the Art Institute and spend more time there than I previously had 40 years before.
There it was; the painting, clearly still the centerpiece of the Institute's collection.