1999 S10 headlights stuck on

For the most parts the truck is in reasonable shape, the only real glitch is that the headlights, tail lights and instrument lights are always on regardless of switch position. I first thought it was the headlight relay, but that wouldn't explain the other lights. I can only assume it's the switch itself. The really odd part is that the lights all turn off with the key off, and I thought that circuit was always hot. I didn't notice any hacked wiring, so I assume that part is OK. Has anyone else had a similar problem? Thanks...