It’s that time of year again when more than a million green-clad revelers fill the streets of America’s most Irish big city for the South Boston St. Patrick’s Day parade, celebrating the heritage and contributions of all those who hail from the Emerald Isle.

Sunday’s parade dates back to the turn of the 20th century and marks both St. Patrick’s Day and Evacuation Day, which commemorates the day in 1776 when British troops left Boston after a protracted siege during the Revolutionary War.

The 3.5-mile (5.6-kilometer) parade rolls through the neighborhood South Boston, a center of Irish-American heritage in a city where more than 1 in every 5 people are of Irish descent. The South Boston Allied War Veterans Council organizes the parade and this year’s chief marshal is retired Navy Lt. Cmdr. Alanna Devlin Ball, who grew up in the neighborhood and represented the U.S. at the 2023 Invictus Games in Germany where she took home gold in powerlifting.

“Lt. Cdr. Devlin Ball’s 12 years career in the Navy serves as an inspiration to young women who seek to serve in today’s military. We are grateful for her service, sacrifice and power of example,” said U.S. Rep. Stephen Lynch, a South Boston native.

The parade is scheduled to kick off slightly earlier in the morning than normal. Last year’s events were marred by violence and public intoxication that officials say they hope to curb on Sunday.

The goal of the parade is “keeping alive the tradition of honoring heritage and service,” the war veterans council said in a statement.

The parade also has been a source of political controversy in years past. The South Boston Allied War Veterans Council banned gay rights groups from marching in the parade up until a decade ago and a U.S. Supreme Court ruling upheld that right in the 1990s.

Two gay and lesbian groups joined the parade in 2015. Organizers for one of the groups, Boston Pride, heralded the move as a point of progress at the time.

Chicago held its St. Patrick’s Day parade on Saturday. Philadelphia also celebrates on Sunday and New York City holds its parade Monday.