Thank you everyone for your help.
I think it was the battery:
The battery would charge up to 12.9 volts, but after 24 hours unhooked from the truck and charger it would decrease to 12.0 or less and would not crank the truck. I charged the battery one more time and had it tested at O'Reilly with a handheld tester that said it "passed". The battery was 3 years old and out of warranty so I made the decision to replace it and remove the battery as a variable in the troubleshooting process. I hooked up the new battery and let the truck sit for 48 hours after which it fired right up. So, hopefully the new battery has solved the problem.
Really weird though the handheld tester said the old battery was good. Especially since it wouldn't hold a charge for 24 hours when it wasn't hooked up to anything.
Thanks again everyone for your comments, they were helpful. I'm hopeful this issue is resolved.