Titles of Grand Lodges in the United States vary. Some are called A.F. & A.M., which means Ancient Free and Accepted Masons. The other most commonly used title is F. & A.M., or Free and Accepted Masons.
The reason for this difference is that in England when Grand Lodges first started, there was a rivalry between two factions of Masons. One faction adopted the title "Ancient" and the other did not. This carried over to the United States where both titles are still in existence.
Two other titles exist in America. Masons in South Carolina call themselves A.F.M. - Ancient Free Masons. Those in the District of Columbia call themselves F.A.A.M. - Free and Accepted Masons. But no matter what the title, all lodges work toward the same end.