Factual error: The Liberty Bell is depicted ringing as the Declaration of Independence is being signed on July 4 (a mistake itself) in the film. The bell actually did not ring on that date, but on July 8, when the Declaration had been returned from the printer and unveiled to the public.
Continuity mistake: Near the end of "The Lees of Old Virginia," Richard Henry Lee is seated on a water fountain, and then stands up. In the following shot from behind, he is back on the fountain and stands up again.
Deliberate mistake: In the film, Martha Jefferson visits Thomas in Philadelphia. While this is factually inaccurate (she was actually at home recovering from a miscarriage), it was changed for the sake of drama.
Continuity mistake: Look very closely when Mr. Thomson is taking the vote by a show of hands on whether or not to make the vote on independence unanimous. Of the delegates who say nay, Thomson points to the direction of Adams first, however, Hopkins is the first delegate shown. Thomson points to the direction of Hopkins last, but Adams is the last delegate shown. Maybe this part was reversed, or the filmmakers screwed up.
Visible crew/equipment: At the end of 'Sit Down John' as Adams is walking out of the Assembly Room, you can see a crew light reflected in the tally/vote board behind him. It's also rather bright in a room, at night, that is only supposed to be lit by candles.
Factual error: During "The Lees of Old Virginia", Richard Henry Lee refers to Harry Lee as "Lighthorse Harry Lee". Harry didn't earn that nickname until 1778.
Chosen answer: By "the British Crown" he meant the king. By "the British half Crown" he was just referring to the money in use by the British at the time.
Exactly contrasting loyalty to the country with loyalty to profit.