At times history and fate meet at a single time in a single place to shape a turning point in man’s unending search for freedom. So it was at Lexington and Concord. So it was a century ago at Appomattox. So it was last week in Selma, Alabama.
There, long-suffering men and women peacefully protested the denial of their rights as Americans. Many were brutally assaulted. One good man, a man of God, was killed.
There is no cause for pride in what has happened in Selma. There is no cause for self-satisfaction in the long denial of equal rights of millions of Americans. But there is cause for hope and for faith in our democracy in what is happening here tonight.
For the cries of pain and the hymns and protests of oppressed people have summoned into convocation all the majesty of this great Government — the Government of the greatest Nation on earth.

Lyndon B. Johnson (1908-1973) American politician, educator, US President (1963-69)

Speech (1965-03-15), “The American Promise,” Joint Session of Congress [04:25]
    (Source)

A nationally broadcast address, introducing the Voting Rights Act of 1965. The mention of Selma is in reference to the events of "Bloody Sunday" on 7 March 1965.