Americans from sea to shining sea united for a joyous celebration 250 years in the making as the Land of the Free marked a quarter-millennium of independence — and the birth of the once-radical notion to guarantee each and every inhabitant life, liberty and the pursuit of happiness.

President Trump kicked off America’s 250th birthday party Friday with a visit to Mount Rushmore in South Dakota as a prelude to his “Salute to America” bash in the nation’s capital.

Supersonic jets are set to scream across the skies over Washington throughout the afternoon and evening Saturday, culminating with flyovers by Trump’s new Air Force One and a B-1 stealth bomber, scheduled for just after the president speaks, followed by a world record-smashing fireworks spectacle.

Trump’s remarks are expected to be a mix of reflection on the last 250 years as well as outlining his vision for the next 5, 10 or 15 years.

New York City has also been a hotbed of patriotic festivities, and revelers both local and from out of town are out in force and ready to party like it’s 1776.

Wendell Mackey, 64, who was in New York City for the first time ever specifically to celebrate America’s milestone moment with his wife, Heather, 63, was showing off his love of the country with a T-shirt festooned with Old Glory — and for a very good reason.

“My grandparents fled Hitler before World War II and came through Ellis Island and America welcomed them and gave them a home. If it wasn’t for them and if it wasn’t for America, I wouldn’t be here.”

Wendell, who is of Polish descent, said the occasion of the United States’ 250th birthday is so big it’s become a global affair.

“I’ve met people from Australia, Japan and Germany who told me they are here to celebrate our anniversary with us. That makes me feel proud, even with different lifestyles, different backgrounds we mesh together, we come together and celebrate together,” he said.

“I’m just proud to be an American, a country that changes the world and gave my grandparents a chance. They came with nothing, and they made it. With hard work you can make it in America.”

Irfaan Jawad, 60, a cab driver who came to the US from Pakistan with his family 11 years ago, including four children, is a living embodiment of the American dream.

He got his citizenship on May 7, 2021, and today he’s a grandfather.

“I work hard. My children get to go to college. I have a better life here and my children will have better life than me,” the Long Island resident told The Post.

“It was a blessing. It was a big change in my life when I came here. It improved my life. I will be working but I will never forget that America gives me this good life,” he said.

“I wasn’t born here, but I am an American.”

Here’s the latest on America’s 250th Anniversary:

• George Washington’s prayer for America still resonates 250 years later
• Where to play and party like it’s 1776 this weekend
• Trump Accounts launch July 4, giving newborns $1,000. Here’s what to know
• Mamdani to deliver America’s 250th speech hours ahead of Trump
• Dunkin’s America 250 eagle cup sparks frenzy as fans race to snag one

Gotham will be rolling out the red, white and blue carpet for some truly once-in-a-lifetime spectacles.

Vice President JD Vance will headline Sail 4th 250, a historic gathering in New York Harbor of military aircraft, tall ships and naval vessels from the US and more than 20 other nations.

A preliminary parade of 24 tall ships sailed down the East River from the Long Island Sound on Friday, but Saturday’s Grand Parade of Sail will see a jaw-dropping fleet of 43 Class A tall ships and 22 Class B vessels from around the world.

They will sail under the Verrazzano-Narrows Bridge, past the Statue of Liberty and up the Hudson River to the George Washington Bridge — led by “America’s Tall Ship,” the USCGC Eagle.

More than 100 of the Navy’s Blue Angels will take flight above the Port of New York to lead the International Aerial Review, and the start of Fleet Week, which was pushed back to coincide with the birthday celebration — will see city streets dotted with convivial sailors.

Times Square is also hosting the first ball drop ever held outside of New Year’s Eve, lowering a ball to mark the stroke of midnight July 4 in all eight US time zones.

The first ball drop came at 10 a.m. EDT on Friday to mark midnight in Guam, and the last drop will occur at 7 a.m. July 4 for American Samoa.

The Macy’s July 4th fireworks show is promising to “illuminate New York City’s iconic skyline with a kaleidoscope of color” as it celebrates its own 50th anniversary.

“The company’s annual summer celebration will feature 12 high-tech pyro animations, an inverted rainbow from the Brooklyn Bridge cable and a quarter-mile-long silver waterfall that will cascade from the bridge to the East River below, as well as a 1,600-foot-wide USA flag in the sky,” Macy’s said.

Along the banks of the Hudson River Friday, early celebrants were taking in the view and soaking up some serious rays.

On Pier 57 Friday, Alex Rotsettis, 57, was tough to miss, decked out in American flag shorts, a T-shirt emblazoned with the Statue of Liberty and proudly proclaiming he was in town to “celebrate life, liberty and the pursuit of happiness” from Florida’s Gold Coast.

“I’ve got family members, grandparents that fought in conflicts and sacrifices that they made to make things possible for all of us here in this country — I honor that. They mean the world to me,” he shared.

“When you’re in the city of New York, you take a look around, you see the Statue of Liberty, you see the diversity here, just for all this to be possible … this is the dream of our forefathers, and here we are. Lots to be thankful for.”

He then let loose with a hearty “happy birthday, America!” which he called “the greatest place on Earth.”

Nancy Sidow, 67, came to the Big Apple with her husband, Kevin, to be a part of the celebration.

“It’s very exciting. I missed the 200th anniversary in 1976 because I was an exchange student and out of the country,” she said.

“I am looking forward to being with the people of New York, who are so diverse, people from all different countries.”

Being in New York City for America’s semiquincentennial had Kevin feeling pensive.

“In a time like this, it makes you reflect on what we have gone through to make our families great and what we’ve gone through to make this country great, how each generation has built on the success of the other and how the country gets better and better,” he said.

“We’re proud to be Americans because we are free. We have the freedom that nobody else has. We are free to articulate our differences.”

For some, simply being there to celebrate America on its birthday sparked strong emotions.

Sue Brown, 61, a retired medical technician from Winchester, Virginia, was moved to tears as she spoke of her love for America and our troops, and said being in New York for the 250th was on her bucket list.

“I’m thrilled. I’m excited to see the big ships,” she said, referring to Saturday’s show-stopping Grand Parade of Sail, which she’ll be watching from the New Jersey side of the Hudson.

“America’s 250th anniversary! How awesome is that? And I get to celebrate it in the best city in the world — New York City,” she gushed.

“I love being an American. There is no country like ours,” she said, starting to tear up.

“Oh, l just love, love her so much.”