I had to do a little research, because didn't know anything about the rhyme. Then I found out it was a poem and I needed to find out who wrote it and apparently, it was Jean Marzollo!
The reason for the exclamation was because she was in charge of all the I Spy books too. How cool!
Here's more information specifically about the book, In 1492.
In fourteen hundred ninety-two
Columbus sailed the ocean blue.
He had three ships and left from Spain;
He sailed through sunshine, wind and rain.
He sailed by night; he sailed by day;
He used the stars to find his way.
A compass also helped him know
How to find the way to go.
Ninety sailors were on board;
Some men worked while others snored.
Then the workers went to sleep;
And others watched the ocean deep.
Day after day they looked for land;
They dreamed of trees and rocks and sand.
October 12 their dream came true,
You never saw a happier crew!
“Indians! Indians!” Columbus cried;
His heart was filled with joyful pride.
But “India” the land was not;
It was the Bahamas, and it was hot.
The Arakawa natives were very nice;
They gave the sailors food and spice.
Columbus sailed on to find some gold
To bring back home, as he’d been told.
He made the trip again and again,
Trading gold to bring to Spain.
The first American? No, not quite.
But Columbus was brave, and he was bright.