(AP) -- Civic leaders, activists, artists and others are celebrating, marching and paying homage Monday to Martin Luther King Jr., marking the 30th anniversary of the federal holiday honoring the slain civil rights leader.

In South Carolina, civil rights leaders planned a march to their state capitol as in past years when their rally highlighted calls to remove the Confederate flag from Statehouse grounds.

The King Day at the Dome gathering began in 2000 with that call. Last July, organizers got their wish as South Carolina swiftly removed the flag which had flown at the capitol for more than 50 years after what police said was a racially motivated shooting that claimed nine lives at a church in Charleston.

The state NAACP said there is still more work to do to honor King and the theme of this year's rally is "education equity," with speakers calling for South Carolina to spend more money to help students in poorer, more rural school districts, which frequently have a majority of black students.

And this year's event will also include appearances by all three main Democratic presidential candidates -- Hillary Clinton, Bernie Sanders and Martin O'Malley.

The rally in Columbia is one of many planned nationwide recalling the legacy of King, who was assassinated in 1968.

Elsewhere, the King Center in Atlanta is set to celebrate the holiday with a remembrance ceremony at Ebenezer Baptist Church. That commemoration caps more than a week of events meant to celebrate the slain civil rights icon's legacy under the theme: "Remember! Celebrate! Act! King's Legacy of Freedom for Our World."

"What most people around the world want, whatever nation they live in, is the freedom to participate in government, the freedom to prosper in life and the freedom to peacefully coexist," said King's daughter, the Rev. Bernice King.

The theme of freedom is especially meaningful this year, she said, because it is the 50th anniversary of her father's trip to Chicago to highlight the need for open and fair housing. King and the Southern Christian Leadership Conference in January 1966 had announced plans for the Chicago Freedom Movement. In a nod to that legacy, Secretary of Housing and Urban Development Julian Castro was set to speak at Monday's service.

King's legacy will also be celebrated in New York at the state Capitol complex. A free program at the Empire State Plaza Convention Center on Monday was to feature musical and theatrical tributes, including performances by Grammy-winning gospel singer Dorinda Clark-Cole and blues guitarist Guy Davis.

And in Minneapolis, activists with the group Black Lives Matter planned to march onto a Mississippi River bridge that connects Minneapolis and St. Paul during a Martin Luther King Day rally.

The Star Tribune reports that the activists would rally for the release of a video of the November fatal shooting of 24-year-old Jamar Clark by a Minneapolis police officer. In St. Paul, protesters want the case of Marcus Golden reopened. Golden was fatally shot by St. Paul police early last year. A grand jury declined to indict the officers involved in that shooting.