[Barrier Blue]

I pulled my 66 GTO out yesterday so I could clean and straighten up the garage. I let it sit in the driveway and run for about 15 or 20 minutes before shutting it off.
When I later tried to restart it to put it away, it cranked but didn't start on the first turn of the key. Tried it again and it was totally dead - no noise from the starter. Then I noticed that the domelight wasn't on. Tried headlights, turn signals, radio, heater fan, rear defroster- nothing worked. Tried the horn, and it worked fine. The horn is the only thing getting juice evidently.
Put the charger on it, even though I didn't think that that would help, and it didn't.
I'm not an electrical whiz by any means, but I'm thinking maybe my ignition switch went bad. I couldn't smell, see, or feel any fried wires.
I had forgotten all about this, but a few months ago I pulled the car out of the garage to let it run for awhile, and it sat there running fine. Then suddenly with no warning it shut off by itself. I was able to start it right back up though.
Can anybody help me with this problem? :

When I'm paid, I always follow my job through...you know that.