yes, I would say so. The other HMGS East conventions are almost as big - Fall In in November:
FALL IN!® 2016. Nov. 4 - 6, 2016. Theme: Poland Through the Ages, From Duchy to Republic
Lancaster Host Resort & Conference Center, Lancaster, PA (but only 3 days, Sunday is usually slow for all three, as most of us drive (or fly) many hours and have to bwe at work the next day)
COLD WARS 2017 March 16 - 19, 2017. Lancaster Host & Resort, 2300 Lincoln Highway East, Lancaster, Pennsylvania 17602-1114, United States. Note that snow storms are a decided possuibility even in late March. 4 day convention. Venue is presently troubled and it's future uncertain, but thus far it seems the event WILL be held there in 2017 once again.
Having said that, although Lancaster is considerably closer to me ( about 4.5 hrs drive vs 7 hrs, and a much easier drive as well), Historicon is the one show I go to every year. . MUCH history there and within a 1-2 hrs drive of Fredericksburg! While there is no official limit on fantasy, Sci-Fi, etc, games, usually 80% of the 500 plus games run at these shows are ":Historical", at least in the broad sense of the word. as you'fre doubtless aware, at US shows, all the games are PLAYED, none are just for show (or even closed to outsiders). Many people play in 2-3 games in a day! It is exceptionally rare to see a GW game at any of these three conventions.