See the context of this sign.

Mount Borah

Idaho's highest peak, 12, 662 feet, is
named for William E. Borah, who
served in the United States Senate
from 1907 until his death in 1940.

Ten or a dozen large but shallow inland seas
have covered this area in the past billion years.
They became a graveyard for countless generations
of sea creatures: bones, shells, coral, and
microscopic remains piled up through the eons
into a clay-and-limestone desposit thousands
of feet thick. During the past 10 or 20
million years, part of this deposit has been
thrust upward into the towering ridge
which you see before you.

Don't miss the rest of our virtual tour of Custer County in 3748 images.