WASHINGTON — Sen. Susan Collins of Maine has sponsored the planting of a tree on the U.S. Capitol grounds in honor of a black teen whose killing in 1955 was an important moment in the Civil Rights movement.

The sycamore tree was planted in honor of Emmett Till on Monday.

Participants include U.S. Attorney General Eric Holder; Mississippi Sens. Thad Cochran and Roger Wicker; and Janet Langhart Cohen, author of a play featuring Emmett Till and wife of former Maine Sen. William S. Cohen.

Till, who was from Chicago, was killed at age 14 after he allegedly whistled at a white woman while visiting family in Mississippi. His mother chose to have an open casket at his funeral, and the civil-rights movement was galvanized after Jet magazine published photos of his mutilated body. An all-white jury acquitted two white men of murder.

Cochran said the tree is a reminder of Till’s role in “heightening America’s awareness of the injustice of racial discrimination.”