Listen to Duffster here.
All other info is terrible. Where do people get their bad info from?! The CDL rules are quite simple.
The Federal standard requires States to issue a CDL to drivers according to the following license classifications:
Class A -- Any combination of vehicles with a GCWR of 26,001 or more pounds PROVIDED the GVWR of the vehicle(s) being towed is in excess of 10,000 pounds.
Class B -- Any single vehicle with a GVWR of 26,001 or more pounds, or any such vehicle towing a vehicle not in excess of 10,000 pounds GVWR.
Class C -- Any single vehicle, or combination of vehicles, that does not meet the definition of Class A or Class B, but is either designed to transport 16 or more passengers, including the driver, or is transporting material that has been designated as hazardous under 49 U.S.C. 5103 and is required to be placarded under subpart F of 49 CFR Part 172 or is transporting any quantity of a material listed as a select agent or toxin in 42 CFR Part 73.