Keith Miller, in his book "Voice of Deliverance: the language of Martin Luther King and its sources" noticed the strong similarities between the conclusion of King's famous "I have a Dream" speech and a speech given by Archibald Carey at the Republican National Convention in 1952. Carey was a correspondent of King's.
Archibald Carey's Speech @ Republican National Convention, 1952
We, Negro Americans, sing with all
loyal Americans:
My country 'tis of thee,
Sweet land of liberty,
Of thee I sing.
Land where my fathers died,
Land of the Pilgrims' pride
From every mountainside
Let freedom ring!
That's exactly what we mean--
from every mountain side,
let freedom ring.
Not only from the Green Mountains
and White Mountains of Vermont
and New Hampshire;
not only from the Catskills
of New York;
but from the Ozarks
in Arkansas,
from the Stone Mountain
in Georgia,
from the Blue Ridge Mountains
of Virginia
--let it ring not only for the minorities
of the United States, but for the disinherited
of all the earth--may the Republican
Party, under God, from every mountainside,
LET FREEDOM RING!
King's "I Have a Dream speech"
Washington Monument, 1963
This will be the day when all of God's children will be able to sing
with new meaning:
My country 'tis of thee,
Sweet land of liberty,
Of thee I sing.
Land where my fathers died,
Land of the Pilgrim's pride,
From every mountainside
Let freedom ring!
So let freedom ring
from the prodigious hilltops
of New Hampshire.
Let freedom ring from the mighty mountains
of New York.
Let freedom ring from the
heightening Alleghenies of Pennsylvania,
Let freedom ring from Stone Mountain
of Georgia.
Let freedom ring from Lookout Mountain
of Tennessee.
Let freedom ring from every hill and molehill
in Mississippi.
From every mountainside,
let freedom ring!