Thou shalt no more be termed Forsaken; neither shall thy land any more be termed Desolate: but thou shalt be called Hephzibah, and thy land Beulah: for the Lord delighteth in thee, and thy land shall be married. - Isaiah 62:4
In the Torah and Old Testament, Beulah is the land of Israel. A blessed place. "Thy land shall be married" is taken to mean that the land will be favoured in the eyes of God.

Also, Merriam-Webster had this entry for Beulah:
  An idyllic land near the end of life's journey - Bunyan's Pilgrim's Progress.

In Hebrew, Beulah means 'married.' John Bunyan uses this theme for his town of Beulah in Pilgrim's Progress (thanks to Tiefling for that bit)

an excerpt from Pilgrim's Progress:
"Now I saw in my dream, that, by this time, the pilgrims were got over the Enchanted Ground, and entering in the country of Beulah, whose air was very sweet and pleasant; the way lying directly through it, they solaced themselves there for a season. Yea, here they heard continually the singing of birds and saw every day the flowers appear in the earth, and heard the voice of the turtle in the land."