While King's birthday is January 15, it is traditionally marked on the third Sunday in January, known affectionately as "King Sunday" in his birthplace of Atlanta, Georgia.
The mood was jubilant at many black churches on Sunday as congregations joined in singing "We shall overcome" and preachers hailed Obama's victory as a monumental step towards the realisation of King's dream for racial equality in America.
"Praise the Lord as we look forward to Tuesday," said Rev Raphael G Warnock, pastor at Ebenezer Baptist Church in Atlanta, where King preached for several years before his assassination in 1968. "We ought to all celebrate this morning ... that we've moved closer to who we say we are," he was quoted as saying by the Associated Press.
Carol Bell-Daniel, a 30-year-old mother of two, was one of several hundred worshippers at a memorial service for King at Mount Zion Baptist Church in Seattle on Sunday.
"It's as if we're moving from the past into the future, realising Martin Luther King's dream," she said, according to the Seattle Post Intelligencer.
Obama's former pastor, the controversial Rev Jeremiah Wright, meanwhile, drew large crowds to a sermon he gave on Sunday at Howard University in Washington DC.
He praised the incoming president, who had distanced himself from the fiery preacher after sermons emerged online in which Wright was heard saying "God damn America" and slamming the US for its racism and foreign policy.
Drawing from passages in the Gospel of John in which the sick overcome their infirmities, Rev Wright declared, "No more seeing ourselves through the eyes of people who don't look like us! How does God see us?"
Worshippers also used Sunday's services as an opportunity to pray for Obama when he takes up office on Tuesday.
The President-elect was himself in church on Sunday after a brief but sombre wreath-laying service to remember the nation's war dead at America's venerated Arlington Cemetery.
Obama and his family received ecstatic applause when they entered Nineteenth Street Baptist Church in northwest DC and took up their specially reserved seats in the second row.
Offering a word of advice for the road ahead, the church's pastor Derrick Harkins told Obama to turn to God for help in times of difficulty.
"Understand that God has prepared you, and God has placed you, and God will not forsake you," he was quoted as saying by the Associated Press.
Bruce Springsteen, Bono, Beyonce, Tom Hanks and Denzel Washington were among the big names who turned out on Sunday night to celebrate Obama's pending inauguration at a memorial concert in front of Abraham Lincoln's statue.
The concert was attended by Obama and his wife Michelle, as well as Vice President-elect Joe Biden and his wife, Jill.
An estimated two million people turned out to cheer on Obama and celebrate with the stars what they anticipate is the start of a new era in American politics.