Lunacon is the annual science fiction convention of the New York Science Fiction Society, also known as the Lunarians. Running annually since 1957 with the singular exception of 1964, it often coincident with Pi-day (March 14th, or "3.14") or St. Patrick's Day (March 17th). It has a membership which typically fluctuates between 800 and 1200.
Lunacon has an ongoing relationship with alumni of the prestigious Bronx Science High School, who treat the convention as a yearly reunion of sorts. In anticipation of future student attendance from schools in the densely populated New York City area, the convention has recently increased and diversified its youth track, known as "Lunacon NextGen", into three categories: Little Lunys (up to age 6), Camp Luny (ages 6-12), and Luny U (ages 12 and up).
This convention lays a plausible and so far uncontested claim of being the first US-only convention to support Anime with a full room for programming/videos. This was in 1983, several months before Yamatocon, the first known US Anime convention. The only additional prior examples uncovered (from memory in interviews, not in citable sources, sadly) were the Worldcon in '1980 (arguably not a "US-only" convention, as by that time it had already been held in Canada, the UK, Germany, and Australia), and an unspecified commercial expo which provided some space for Anime programming, but not a dedicated room.