http://archive.uschess.org/beginners/uscffaq.php
The USCF Mission Statement: The United States Chess Federation (USCF or US Chess) is a not-for-profit membership organization devoted to extending the role of chess in American society. USCF promotes the study and knowledge of the game of chess, for its own sake as an art and enjoyment, but also as a means for the improvement of society. It informs, educates, and fosters the development of players (professional and amateur) and potential players. It encourages the development of a network of institutions devoted to enhancing the growth of chess, from local clubs to state and regional associations, and it promotes chess in American schools.
To these ends, USCF offers a monthly magazine, as well as targeted publications to its members and others. It supervises the organization of the U.S. chess championship, an open tournament every summer, and other national events. It offers a wide range of books and services to its members and others at prices consistent with the benefit of its members.
USCF website www.uschess.org is where you sign up membership, search for tournaments, and check your rating.