The first Earth Day on April 22, 1970, drew crowds of thousands in cities, on campuses, and in public parks, such as this one, around the U.S.

Artist Pablo Solomon, taught earth science at "an inner-city school" in Houston in 1970. Earth Day events in Texas, he said, gave him hope that his lessons might find their way into the world at large.

"I can remember how excited I was that there was going to be this effort to draw attention to conservation and environmental preservation on a global scale," he said in an email. "The young people that went to the Houston school in which I taught were lucky to see nature on a vacant lot, much less on a rainforest scale. But even they seemed to understand what a good thing it would be to live in harmony with nature.

"At that time the Houston Ship Channel was so polluted that it would literally burn on the surface and chemical vapors released from the oil refineries would peel the paint off of cars overnight."