U.S. President Barack Obama will speak at the Edmund Pettus Bridge in Alabama Saturday to mark the 50th anniversary of the civil-rights march from Selma to Montgomery, during which police brutally attacked 600 unarmed demonstrators. It’s Obama’s first trip to Selma since he took office in 2009.

Peaceful protesters began the first of three marches to walk the 54-mile highway from Selma to Alabama’s state capital March 7, 1965. It was nicknamed Bloody Sunday after state troopers violently attacked the civil-rights demonstrators with clubs, whips and tear gas. The violence sparked national outrage, with Martin Luther King Jr. seeking federal protection for the Selma marchers and a new federal voting-rights law to enable African-Americans to vote without harassment. The Voting Rights Act, a landmark piece of civil-rights legislation that prohibits racial discrimination in voting, was signed into law in August of that year , according to the National Voting Rights Museum and Institute in Selma.

“Selma is not just about commemorating the past, it’s about honoring the legends who helped change this country through your actions today, in the here and now,” Obama, the first black U.S. president, said at South Carolina’s Benedict College Friday. “Selma is now.”

Today, the route from Selma to Montgomery is memorialized as a U.S. National Historic Trail. Almost 100,000 people are expected to re-enact the march Saturday, WSB-TV in Atlanta reported.

The president will be joined by first lady Michelle Obama and their teenage daughters, Malia and Sasha, at the Edmund Pettus Bridge where King and civil rights leaders walked 50 years earlier, CBS News reported. Obama was expected to deliver remarks at 12:15 p.m., but his speech likely will be delayed due to an incident at the White House in Washington Saturday morning. Watch a live stream of his speech in Selma below: