A huge oil spill. A river catching fire. Lakes so polluted they were too dangerous for fishing or swimming. Air so thick with smog it was impossible to see the horizon.

That was the environmental state of the nation 50 years ago. But pollution and disasters prompted action. On April 22, 1970, millions of people throughout the country demonstrated on the inaugural Earth Day, calling for air, water and land in the country to be cleaned up and protected. And that year, in a bipartisan effort, the Environmental Protection Agency was created and key legislation — the Clean Air Act, the Clean Water Act and the Endangered Species Act — came into force. 

Now, the Trump administration has made eliminating federal regulations a priority, and an increasing number of environmental rules are under threat.

Here’s a look at five environmental disasters that shifted the public conversation and prompted, directly or indirectly, lawmakers to act.