WASHINGTON — US President Joe Biden on Tuesday signed into law a bill finally making racist lynchings a federal hate crime, ending more than a century of delays in outlawing the symbol of what he called “pure terror.”

Anyone convicted under the new law will face up to 30 years in prison, ending a history of impunity over what researchers say were thousands of lynchings — often unpunished — between the end of the Civil War in 1865 and 1950.

The bill is named after Emmett Till, a 14-year old African American whose brutal murder galvanized the US civil rights movement in the 1950s.

Biden was joined at the Rose Garden ceremony by Vice President Kamala Harris, the first Black woman in the post, and Michelle Duster, the great-granddaughter of pioneering Black journalist and anti-lynching campaigner Ida B. Wells.

“Lynching was pure terror,” Biden said, recounting the horrific practice of public vigilante killings of mostly African Americans, often in front of enthusiastic white crowds in the post-slavery United States.

Biden, however, warned that “racial hate isn’t an old problem. It’s a persistent problem” and that “hate never goes away, it only hides.”

And Harris warned that “lynching is not a relic of the past.”

“Racial acts of terror still occur in our nation,” she said.

The Senate unanimously passed the bill earlier this month, with Democratic Senate Majority Leader Chuck Schumer saying that the long delay in agreeing on a federal measure had been “a stain on America.”

Till was abducted and murdered in August 1955 while visiting relatives in the southern state of Mississippi. The boy’s mutilated body was found three days later in a local river.

This came days after a white woman, Carolyn Bryant, alleged that he had propositioned her in a store and touched her on the arm, hand and waist.

Till’s mother famously insisted that her son’s remains be displayed in an open casket to show the world what had been done.

Two white Mississippi men, Roy Bryant, Carolyn Bryant’s husband, and J.W. Milam, his half-brother, were charged with murder but acquitted by an all-white jury. The pair later admitted in a magazine interview that they had killed the boy.