I saw S&G in concert in July of 1967 at the Red Rocks Amphitheater in Colorado. I was a child, so I do not know the exact date.
The opening act was a 1960s group named the Lovin´ Spoonful (´Summer in the City, Do You Believe in Magic´). Although they were big at the time, the audience wanted to see S&G so much that the Spoonful eventually just walked off the stage. The S&G concert was just the two of them and Paul on guitar. Somewhere I have some 8mm home movie footage of the show, but I haven´t seen it in many, many years.
The next morning, we saw Art in the parking lot of the Holiday Inn. (Had it been Paul, my brother and I probably would have asked for an autograph). Luckily in all the years since, I have had two chances to meet and talk with Paul.