The North American Circuit is a series of fencing tournaments held between October and April of each USFA season, usually 6-8 in number.  These are national tournaments, and there are no NAC qualifying events--any fencer, US or foreign, who meets the age/rating requirements for an event may compete in a NAC in that event simply by registering in advance.

Each category (Division I, II, III, Cadet, Junior, Veteran, Wheelchair, Y14, Y12, Y10) is fenced in two NAC events a season.  The location of the events is spread throughout the United States to facilitate each fencer (hopefully) being in the vicinity of at least one NAC meet a season.

Some of the NAC events (Division I, Junior, Cadet) are used in determining USFA National Point Standings.
 

The NAC events are considered "fun" meets--even though they are national competitions and governed accordingly, they are one-shot events that don't really carry the prestige of the Junior Olympics and the National Championships. Much of that probably has to do with the fact that one must first win the right to compete at the latter events through divisional qualifying events or other means.