Katie, don't despair because you haven't got a lot yet. The really knowledgable people haven't checked in yet.
Being a Wisconsinite (UW-'67) I feel a responsibility. Here are my picks from the acoustic side; others know the rock side.
Phil Ochs: What's That I Hear Now
Draft Dodger Rag
I Ain't Marchin' Any More
Pete Seeger: Where Have All the Flowers Gone?
Waist Deep in the Big Muddy
Joe McDonald: I Feel Like I'm Fixin' To Die Rag
Bob Dylan: Blowin' In The Wind
Times They Are A-Changin'
When the Ship Comes In
With God On Our Side
John McCutcheon: Christmas in the Trenches
Malvina Reynolds: It Isn't Nice
What Have they Done to the Rain?
Buffy Sainte-Marie: Universal Soldier
Chet Powers: Let's Get Together
Tom Paxton: The Willing Conscript
Pink Floyd: Just Another Brick in the Wall
Gil Scott-Heron: The Revolution Will Not Be Televised.
You also said ANY era? There's the whole canon of civil rights freedom songs. Also a canon of labor songs. You aren't looking for them, too, are you? Tell your station that you have 2 or 3 more shows for them!!!
Best wishes -- LarryC