More than a million people braved the bitter cold in Washington to see Barack Obama take the oath of office as America's 44th President, millions more around the world watched live TV coverage of the event.
It was a regular work day in Europe and darkness had fallen by the time Barack Obama took the oath of office, but that did not diminish the interest or the eagerness with which so many Europeans awaited the event.
There were celebrations in the far corners of the world. Feasts were prepared in Kenya, the homeland of President Obama's father; students in the Indonesian capital, Jakarta, gathered to watch the inauguration in the elementary school Barack Obama attended as a child. Black-tie dinners and champagne parties were being held in the capitals of Europe.
Barack Obama has long been a favorite in Europe - young, energetic, full of charisma and words that promised change.
German Chancellor Angela Merkel sent words of congratulations.
"It is a very special day, not only for the United States of America, but a special day also for billions of people all over the world," she said.
Mrs. Merkel said it is historic to have this first African-American president, and she said she looks forward to a strong, intensive trans-Atlantic cooperation.
Her French counter-part, President Nicolas Sarkozy also sent his congratulations.
"We are anxious to see him get to work so we can change the world with him," President Sarkozy said.
French political analyst, Etienne Schweisguth of the prestigious political science university in Paris, said there has been an almost euphoric mood about Mr. Obama.
He said the sentiment in France is a bit like the liberation after World War II - the idea that we are entering a new world, that everything is possible.
Schweisguth acknowledged that this dream of an ideal world may not be realistic, but he said there is a fundamental expectation in France that under Barack Obama, America will find its way again to work for a new world order.
In his inaugural address President Obama outlined the work that must be done, saying the problems are many and complex from a global economic crisis, to wars in Iraq and Afghanistan, to the challenges of strengthening old alliances and building new ones.