It was the only song at the time to ever mention the name "Nixon." And Crosby, Stills, Nash & Young put it out despite knowing it would hurt another tune they already had on the charts. "Ohio," about a deadly protest gone wrong at Kent State University, is now half a century old and it still resonates with many who were around back then. 
 
Esquire Magazine has a story on the creation of the song, including the fact that the group felt so strongly about its contents, that they didn't even worry how it would hurt another of their best selling hits.

"As Crosby told Nash, "I saw Neil walk off with his guitar into the woods. And he comes back an hour later with this song.

"Crosby, Stills and Nash were blown away by Young’s burst of inspiration and decided not only to record the song at once, but to release it as quickly as possible, even though the band was making a sizable financial sacrifice in the process.

“We had ‘Teach Your Children’ (out),” Nash said. “It was already in the top 20. It was going towards the top of the charts. We put out ‘Ohio’ immediately—and killed our own single because we thought it was more important to talk about America killing its own children than having a hit record.”

50 Years Ago Neil Young Wrote a Song That Changed a Generation of Protest Music