This photo released by The White House shows President Bush talking to U.S. troops from Camp David, 22 Nov 2007

President Bush has telephoned several members of the U.S. armed forces in Iraq, Afghanistan and at sea to wish them a Happy Thanksgiving and thank them for their service.

A presidential spokeswoman says Mr. Bush told the service members Thursday that he is impressed with their courage and compassion. The president also said he understands and appreciates the sacrifice the troops are making by being away from their families during the holiday.

Millions of Americans gather today to celebrate the nation's annual Thanksgiving Day holiday.

Volunteer Michael Linderman, right, removes freshly roasted turkeys from pans at Food & Friends in Washington, D.C., 22 Nov 2007

Many Americans travel hundreds, even thousands, of kilometers to spend the day with loved ones and enjoy a huge feast with turkey as the main dish. They also watch traditional nationally televised holiday events, including National Football League games and an annual parade in New York City, sponsored by Macy's department store, featuring musical acts and colorful floats.

Although there is a record of earlier Thanksgiving celebrations, the tradition is often traced back to 1621. That year, British colonists at the Plymouth settlement in, what is now the northeastern state of Massachusetts, held a feast with a Native American tribe, the Wampanaog, who taught the colonists how to grow food and hunt for game in their new home.

The celebration grew during the early years of the United States, and President George Washington proclaimed a national Thanksgiving in 1789 to celebrate the ratification of the U.S. Constitution.

President Franklin D. Roosevelt signed legislation in 1941 that set the annual Thanksgiving holiday for the fourth Thursday in the month.

Three NFL games are on the schedule today, including the Green Bay Packers versus the Detroit Lions, a longtime Thanksgiving Day matchup. The other games include the New York Jets taking on the Dallas Cowboys, and the Indianapolis Colts against the Atlanta Falcons.