Also;
The United States Chess Federation (USCF) awards the Title of National Master to anyone who achieves a USCF rating of 2200, and the title of Senior Master to anyone who achieves a USCF rating of 2400 along with certain performance-based 'norms' during tournament play.
Just thought I'd point that out.
To become a GM, a player must acquire a FIDE rating of a minimum of 2500. Moreover, the player must achieve at least three GM norms or 27 games to be eligible. A GM's score may dip below 2500 during their tournaments. However, they don't have to keep their score at 2500 throughout their career to keep this title.