President Richard Nixon vetoed the Clean Water Act in 1972. But Congress overrode him on a bipartisan vote, and the landmark law to reverse the toxic degradation of U.S. rivers, lakes and streams took effect half a century ago today.

The law was inspired in part by the notorious 1969 Cuyahoga River fire in Ohio, in which the river itself, laden with oil and other industrial pollutants, went up in flames.