Today in history nothing much happened, or at least nothing much happened which interests me. Yes, in 1863 West Virginia joined the Union as either the 35th or the 24th state, depending on whether or not one counts the 11 states of the Secession. But this was more symbolic than significant at the time, and West Virginia remains pretty insignificant to this day. And in 1963 the US and USSR agreed to the establishment of the hotline, to ease communications in times of tension. But this also has, thankfully, proven to be symbolic, as it has never been used "in anger". Actually, its most significant usage has been as a prop in numerous movies, beginning with the dueling apocalyptic classics of Fail Safe and Dr. Strangelove.
Yet speaking of movies, one historical landmark did occur on June 20 1975. That is the release of Jaws, which became the first summer blockbuster film ever. I leave it to you to decide if this was a positive or negative development.