- "You made me a better President, and you made me a better man," he wrote
- The letter highlights memorable highs and lows of the last eight years
"Before I leave my note for our 45th president, I wanted to say one final thank you for the honor of serving as your 44th," he wrote. "Because all that I've learned in my time in office, I've learned from you. You made me a better president, and you made me a better man."
The President recalled tragedies such as the Charleston church massacre and celebrations such as military graduations. He also celebrated gay and lesbian Americans who now have their marriages recognized and ill people who now have access to health care.
Obama went on to challenge voters -- regardless of political affiliation -- to commit themselves to improving the common good.
"I've seen you, the American people, in all your decency, determination, good humor and kindness. And in your daily acts of citizenship, I've seen our future unfolding," he said. "All of us, regardless of party, should throw ourselves into that work -- the joyous work of citizenship. Not just when there's an election, not just when our own narrow interest is at stake, but over the full span of a lifetime."
Obama has said he will remain engaged in issues he cares about in his post-White House life.
"I'll be right there with you every step of the way," he wrote. "And when the arc of progress seems slow, remember: America is not the project of any one person. The single most powerful word in our democracy is the word 'We.' 'We the People.' 'We shall overcome.' "
"Yes, we can," he added.