The House and Senate presented the Congressional Medal of Honor to the families of four girls killed in the 16th Street Church Bombing in Alabama 50 years ago.
Carole Robertson, 14; Addie Mae Collins, 14; Cynthia Wesley, 14, and Denise McNair, 11, were killed in the explosion of a bomb planted outside the church by white supremacists.
The 1963 attack outraged the nation and helped spur passage of the Civil Rights Act of 1964 and the Voting Rights Act of 1965.
"There was no safety for those four little girls. Not even Sunday school," Senate Majority Leader Harry Reid, D-Nev., said. "But there really was salvation. Not only for the four young ladies, but for a nation."
"That outrage sparked by the deaths of these four innocents ignited the Civil Rights Movement like nothing had up to that time," he added.
Sen. Mitch McConnell, R-Ky., noted that while every stained glass window in the church was destroyed, one remained: a window pane depicting Christ leading a group of children.
"The symbolism was potent," McConnell said.
Past recipients of the medal include Rosa Parks, Martin Luther King Jr., and his wife Coretta Scott King.