President-elect Barack Obama said "a very affectionate thanks" to the people of Illinois in a letter published Sunday in the Chicago Sun-Times and other newspapers across his home state, CNN reported.
Vice President Dick Cheney stands with then-Sen. Barack Obama's family in a mock swearing-in in January 2005.
Obama announced on Thursday that his resignation from the U.S. Senate is official as of Sunday.
"Today, I am ending one journey to begin another," Obama's letter said. "After serving the people of Illinois in the United States Senate -- one of the highest honors and privileges of my life -- I am stepping down as senator to prepare for the responsibilities I will assume as our nation's next president."
Obama wrote about moving to Illinois two decades ago "as a young man eager to do my part in building a better America."
"On the South Side of Chicago, I worked with families who had lost jobs and lost hope when the local steel plant closed. It wasn't easy, but we slowly rebuilt those neighborhoods one block at a time, and in the process I received the best education I ever had," he wrote.
Obama followed his years as a community organizer and lawyer with a successful bid for the Illinois state Senate.
"It was in Springfield, in the heartland of America, where I saw all that is America converge -- farmers and teachers, businessmen and laborers, all of them with a story to tell, all of them seeking a seat at the table, all of them clamoring to be heard. It was there that I learned to disagree without being disagreeable; to seek compromise while holding fast to those principles that can never be compromised, and to always assume the best in people instead of the worst," his letter said.
His letter recalled people he met in his travels around the state during his run for the U.S. Senate four years ago.
"I still remember the young woman in East St. Louis who had the grades, the drive and the will but not the money to go to college. I remember the young men and women I met at VFW halls across the state who serve our nation bravely in Iraq and Afghanistan. And I will never forget the workers in Galesburg who faced the closing of a plant they had given their lives to, who wondered how they would provide health care to their sick children with no job and little savings," he wrote.
Obama said his memories of the people of Illinois "will stay with me when I go to the White House in January."
"The challenges we face as a nation are now more numerous and difficult than when I first arrived in Chicago, but I have no doubt that we can meet them. For throughout my years in Illinois, I have heard hope as often as I have heard heartache. Where I have seen struggle, I have seen great strength. And in a state as broad and diverse in background and belief as any in our nation, I have found a spirit of unity and purpose that can steer us through the most troubled waters," he wrote.