The historical basis for much of Glenn Beck's material is W. Cleon Skousen. Beck wrote the foreword for Skousen's The 5000 Year Leap, and Skousen's other work, The Making of America, is pretty insane and awful. For example, according to Mother Jones:
Skousen quotes liberally from an essay on slavery by Fred Albert Shannon. According to Shannon, slave families were usually sold as a unit to keep them contented, but sales were actually beneficial to the slaves, since it improved their sense of self-worth. Slaves' marriages were "impermanent," but that was merely "one of the blessings of the slavery." In fact, Shannon notes, many slaves preferred slavery to freedom.
And...
Meet the founding brothers: Hengist and Horsa, fifth-century Anglo-Saxon kings. According to Skousen, the Anglo-Saxons—and by extension our own WASPy Founding Fathers—were descended from one of the Lost Tribes of Israel, in effect making them a divine people. This easily debunked assertion is the foundation of the white supremacist "Christian Identity" movement.
A couple of weeks ago, Beck was criticizing the Jamestown settlers as being communists. Weird, I know. A McCarthy style witch hunt against people from 400 years ago. Whatever. The historical backing for this Beck rant appears to come from Skousen's The Making of America.
One thing is certain: Beck is clearly a disciple of Skousen. Or at least pretends to be.