The nation honored its men and women in uniform Wednesday, especially those who died while serving the country.

Thousands were on hand to salute the troops at the 90th annual Veterans Day Parade, which stepped off at 11 a.m. on Fifth Avenue at 25th Street.

The parade featured 20,000 veterans, civic and youth groups, leaders like Mayor Michael Bloomberg and Governor David Paterson, and more than 3,000 men and women on active-duty – including the crew from the newly-arrived USS New York. A 21-gun salute and a military flyover were also part of the day's event.

"It's very important to be here today," said one parade-goer. "We have to honor our veterans. Everyone should be honored."

"The backbone of America, really, is the men and women who fought for our country," said parade chairman Pat Gualtieri. "So without that, you might as well just forget it all."

"If the nation can show its veterans that they're grateful, then we'll always have young people ready to step up and fill the ranks," said veteran Don Stoud, who marched in the parade.

The city's parade is said to be the largest in the nation.

Earlier in the day at Gracie Mansion in the Upper East Side, the mayor welcomed past and present military members from the city to a pre-parade breakfast.

After a moment of silence for the victims of the Fort Hood massacre, Bloomberg thanked the crowd for their service.

"There's a total of some 240,000 veterans who live in our five boroughs, and I am determined to make sure we can do everything to get them and their careers and lives back on track and let them share in the great American dream that they so valiantly fought for," said the mayor.

Meanwhile, as the president paid his respects on Veterans Day, people all over the country flocked to memorials.

President Barack Obama and First Lady Michelle Obama joined Vice President Joe Biden and his wife Jill at Arlington National Cemetery.

The commander-in-chief placed a wreath on the Tomb of the Unknowns in a ceremony that honors military personnel who have lost their lives in battle and also those who are currently serving.

"In this time of war, we gather here mindful that the generations serving today already deserve a place alongside previous generations for the courage they have shown and the sacrifices that they have made," said the president. "In an era where so many acted only in narrow self-interest, they have chosen the opposite. They chose to serve the cause that is greater than self."

Dozens of people in the nation's capital also gathered at the World War II Memorial and Vietnam Memorial to lay wreaths and remember fallen soldiers.