The stones that make up the main body of the Altar come from all fifty states and from every United States President since Harry Truman. There is a stone from Plymouth, England where the Pilgrims left the Old World and one from Plymouth Rock, Massachusetts where they landed in the new. There are stones from the battlefields of Lexington, Concord, and Yorktown where the American Revolution began and ended. Three stones from the Parthenon in Athens and a stone from the ancient Colosseum in Rome are also embedded in the altar.
Three large slabs of "verde antique," also known as "Maryland Green," marble form the top of the Altar. The slabs weigh more than half a ton each. They come from a quarry in Maryland that straddles the Mason-Dixon line, the boundary separating the north and south during the Civil War. The slabs on the right and the left symbolize the North and the South and the one in the center symbolizes the joining of the two into one Union. Soil from Mt. Zion in Jerusalem is mixed into the mortar that binds the marble to the Altar.
Perhaps the most unusual stone is the one from Koblenz, Germany, the town where Sandy Sloane’s plane was shot down in 1944. In 1969 the mayor of Koblenz made a special trip to the Cathedral and presented a stone from the 600 year old bridge over the Moselle River in Koblenz. The donation of the stone the accompanying service on October 14, 1969 symbolized the Cathedral's ideals of friendship, peace, and brotherhood.