From sea to shining sea

Meaning
From one coast to another.

Origin
Taken from a line in 'America the Beautiful', the patriotic song written by Katharine Lee Bates in 1893. She wrote other versions later, in 1904 and 1913.

O beautiful for spacious skies,
For amber waves of grain,
For purple mountain majesties
Above the fruited plain!
America! America!
God shed his grace on thee
And crown thy good with brotherhood
From sea to shining sea!

She wrote the song following an inspirational visit to Pikes Peak, Colorado, USA, which she later described thus:

"One day some of the other teachers and I decided to go on a trip to 14,000-foot Pikes Peak. We hired a prairie wagon. Near the top we had to leave the wagon and go the rest of the way on mules. I was very tired. But when I saw the view, I felt great joy. All the wonder of America seemed displayed there, with the sea-like expanse."

The phrase is also frequently associated with Canada. The Canadian national motto - "A mari usque ad mare", translates as "From sea to sea". This has biblical origin:

"He shall have dominion from sea to sea and from the river unto the ends of the earth." (Psalm 72:8)

Source: http://www.phrases.org.uk/meanings/from%20sea%20to%20shining%20sea.html