"Ohio" was written by Neil Young in reaction to the Kent State shootings of the 4th of May 1970, after he had seen photos of the incident. Released as a single, it had Stephen Stills' "Find the Cost of Freedom" as a B-side.
Neil Young said, "It's still hard to believe I had to write this song. It's ironic that I capitalized on the death of these American students. Probably the biggest lesson ever learned at an American place of learning. My best CSNY cut. Recorded totally live in Los Angeles. David Crosby cried after this take."
"Ohio" wasn't played on major AM radio stations because the song mentions the President at the time, Richard Nixon.
The song was included on the Neil Young compilation albums "Decade" (1977) and "Greatest Hits" (2004).
Information source: https://www.azlyrics.com/lyrics/neilyoung/ohio.html
https://en.wikipedia.org/wiki/Ohio_(Crosby,_Stills,_Nash_%26_Young_song)