Set in 1757 on the Van Alstynes' farm in Guilderland, outside of Albany City, The Matchlock Gun takes place at a time when the state of New York was still a British colony. Young Edward Van Alstyne is fascinated by the Spanish matchlock gun that his greatgrandfather brought from Holland to America. Over six feet long and very heavy, the old-fashioned gun can be fired only by igniting the priming "like a cannon." The action of the story takes place in and around the house in which the Van Alstynes live, not far from the sturdy brick house of Edward's grandmother, the Widow Van Alstyne.

The French and Indian War threatens the safety of the Guilderland community. Edmonds sets a scene of warmth and security in his initial chapters but hints at the danger that will soon intrude upon the domestic haven of the Van Alstynes' house.