While in court, Cilla swears to tell the whole truth, etc. "So help me God." The final "so help me God" phrase was only instituted after George Washington became president, as he added the phrase himself.
As the Redcoats are shown first approaching Lexington Common, their shadows indicate that they are marching west to east. Their route from Boston actually meant that they marched toward Lexington going east to west. Moreover, the shadows in the scene indicate that the sun is well up, however the Redcoats actually arrived at Lexington common at 5:00 AM as day was breaking.
Johnny and Rab are pictured as taking part in both the skirmish at Lexington Common and the one at North Bridge in Concord. In fact the colonist groups that fought those battles were two distinct groups of militia.
On the night of April 18th, 1775, Paul Revere is shown rowing solo across the Charles River. In fact he had two associates rowing with him. However give kudos to the writers for showing him meeting Deacon John Larkin who actually owned the horse that Revere rode. Revere did not own a horse at the time. And since the British captured Revere in Lexington and took the horse, Deacon Larkin never saw his horse again.
During the last Committee meeting, where Otis gives his impassioned speech, one of the men seated at the table has a large black (paper?) circle visible on the back of his wig. This is visible twice as the camera pans by.