Canadian road signs appear in several scenes including the early scene where Abbie is calling from the isolated phone booth. In the scene where Abbie's mother is driving down the road, a sign written in metric is clearly visible.
The sign behind Abbie Hoffman for the "Chicago 7 Legal Defense Fund" is misspelled "Defence".
Hoffman asks a young soldier what he thought about Jimi Hendrix at Woodstock. Hoffman talks about Jimi playing before half a million people. In fact, Hendrix was one of the last acts to play - on Monday morning of the weekend concert. About 40,000 - 50,000 people were left to see his performance.