Philadelphia (CNN) - Hillary Clinton -- joined by her husband, Bill, and their daughter, Chelsea -- campaigned a final time with President Barack Obama and first lady Michelle Obama Monday night, in front of tens of thousands of supporters before the historic Independence Hall in Philadelphia.

The group celebrated the history Obama made eight years ago, as the first African-American to win the White House, and expressed optimism that the next day Clinton will make a different kind of history as the first woman to be elected to the highest office.

Still hours away from Tuesday morning when polls would open on the East Coast, Obama issued an urgent warning in what would be one of his final and most importance speeches as president.

"The choice you face when you step into that voting booth could not be more clear or could not be more serious," Obama said, moments before the Liberty Bell rang out to mark a new hour.

"If you share my faith, then I ask you to vote," the President said. "If you want a president who shares our faith in America, who's lived that faith in America, who will finally shatter a glass ceiling and be a president for each and ever one of us, then I'm asking you to work as hard as you can this one last day."

Calling his former opponent a fighter, a stateswoman, a mother, a grandmother and a patriot, Obama introduced his former secretary of state to the stage as "our next president of the United States of America."

After a long embrace, Clinton thanked both the President and the first lady for serving the country for eight years with "grace, strength, brilliance and a whole lot of cool."

She said the best way for Americans to express gratitude to the Obamas would be to elect the only presidential candidate committed to preserving Obama's legacy.

"I'm pretty sure as they said tonight, that the best way to thank them is to do something really important tomorrow -- to vote," Clinton said. "As the President just pointed out, there is a clear choice in this election. A choice between division or unity."

Echoing a message she has taken across the country through the general election, Clinton vowed to be "a president for all Americans" -- not just those who support her in this election.

"I believe we all have a role to play in building a better, stronger fairer America; building on the progress that we have enjoyed under President Barack Obama over the last eight years," she said. "I am not going to let anybody rip away the progress we've made and turn the clock back, sending us back in time where people are free to question the foundation of our country."

Monday marked eight years and three days since then-Sen. Obama became the first African-American elected president, after a contentious primary battle against Clinton.

As the Obamas have neared the end of their two terms in the White House, the first couple has emerged two of Clinton's most powerful surrogates as the Democratic nominee has confronted an extraordinary opponent -- Republican nominee Donald Trump -- in an extraordinary election.

First lady Michelle Obama, who has been out on the campaign trail the past few weeks vouching for Clinton, struck a nostalgic tone.

"This is truly an emotional moment for me for so many reasons. We are one day away from once again making history," Obama said. "I am also emotional because in many ways, speaking here tonight is perhaps the last and most important thing that I can do as the country's first lady."

The president, too, reflected on the past eight years, and thanked his supporters for electing a little-known "skinny guy with a funny name."

"Eight years ago, I asked all of you to join me on an unlikely journey," Obama said. "We turned 'yes we can' into 'yes we did.' "