...But A-Kon was not the first con, oh no! Nerd historian Dave Merrill reports on a long-forgotten single-day event called YamatoCon which also took place in Dallas, but seven years prior to A-Kon's 1990 launch. That's right, in 1983, a year before I was even born, Dallas hosted the Star Blazers marathon/dealer room event of YamatoCon 1.
YamatoCon's first year drew 100 attendees and 8 vendors, which is pretty damn good for an anime convention in 1983. The next event YamatoCon didn't take place until 1986, but it saw 300 attendees from as far away as Louisiana, and spawned a more general anime convention.
But even YamatoCon may not have been the first-ever official gathering of anime nerds in the US; Merrill notes a couple of micro-events that took place in 1982 for Star Blazers fans.
All in all, it's a really cool piece of North American anime fan history, so definitely check out the lengthier treatise at Merrill's site.