Boston hoisted the Juneteenth flag over City Hall Plaza on Monday, heralding a week of celebrations and commemoration of the day in 1865 when the news of emancipation finally stretched all the way across the country.

“True freedom is expansive and affirmative, and as the cradle of liberty, Boston doesn’t just recognize that freedom, we are determined to maintain it,” said Mayor Michelle Wu. “The flag we are about to raise is as American as the one with 13 stripes and 50 stars. It is red, white and blue, and it has one star surrounded by its glow, representing the freedom at the core of our democracy.”

City leaders and organizers gathered in the plaza at noon Monday to raise the flag and speak on the meaning of the holiday in Boston.

Juneteenth marks the anniversary of the day on June 19, 1865, when the Union army reached Galveston, Texas, to tell enslaved African Americans of their emancipation. The Juneteenth flag was designed by now 80-year-old Boston activist Ben Haith in 1997.

The Boston area has a host of activities planned to mark the holiday.

Tuesday, June 18 to Friday, June 21: Embrace Boston will host the Embrace Ideas Festival, including a Juneteenth Block Party and the Juneteenth Concert. Tickets are available on the organization’s website.

Wednesday, June 19: The ICA, MFA and the Isabella Stewart Gardner museums, among others, will all offer free admission during the holiday and host workshops, speakers and more.

The Museum of the National Center of Afro-American Artists and Boston Juneteenth Committee will host a series of event on Juneteenth. The celebration will include a flag raising at the Dillaway-Thomas House in Roxbury Heritage State Park at 12:30 p.m., a parade from the park to the Museum of the NCAAA at 2 p.m. and an observance on the museum grounds at 4 p.m.

Brookline For the Culture will host a Juneteenth Block Party in Brookline at the Florida Ruffin Ridley School from 12 p.m. to 4 p.m. featuring free food, face painting, games and more.

The Emancipator will be hosting Historically Black Phrases Live!, a touring game show with trivia based on Black culture, in Boston at WBUR’s CitySpace. Tickets are available for purchase online.

Boston Harbor Islands will host events at Georges Island and the Boston Harbor Islands Welcome Center for Juneteenth from 9:30 a.m. to 5 p.m., featuring live music, a tour on Boston’s Maritime Underground Railroad and more. Events are free but some require the purchase of a ferry ticket.

Friday, June 21: The Winthrop Community Garden will be hosting a Juneteenth celebration from 5:30 p.m. to 7:30 p.m., featuring free food, a drum circle and more at the garden in Roxbury. The event is free but participants can register in advance for updates.