It's #EarthDay.
Earth Day started in 1970. Although San Francisco peace activist John McConnell proposed the first Earth Day in 1969 and said it should occur on the first day of spring in the northern hemisphere, it was the national environmental teach-in sponsored by Senator Gaylord Nelson (D-Wisc.) on April 22, 1970, that caught the public's attention. (Denis Hayes, the organizer running the event for Nelson, hated the name "teach-in". Julien Koenig, a Volkswagon marketing expert, independently came up with the name "Earth Day" for Nelson's event.)
One of the major events which helped Earth Day to come about was the June 22, 1969, fire on the Cuyahoga River in Cleveland. There had been 12 major fires on the polluted river since 1868, and the 1969 fire was the second-smallest. Other rivers had caught fire across the nation over the previous decade, but somehow this one caught the imagination of the press. "Time" made the fire its cover story, although the cover photo was of the huge 1952 fire.
The 1969 Cuyahoga River fire helped ignite (hee hee) the final push for US environmental laws.
Here's a list of the other Cuyahoga River fires (inflation-adjusted for 2020).
The image is of the 1952 fire.