Back in 1892 the Pledge of Allegaince of the United States was composed by Francis Bellany. The pledge was later adopted officially by Congress in 1942 and it not surprisingly contained no reference to God.
Here is the original pledge:
"I pledge allegiance to my Flag and the Republic for which it stands, one nation indivisible, with liberty and justice for all."
By the time it reached official status it had been changed to the following:
"I pledge allegiance to the flag of the United States of America, and to the republic for which it stands, one nation indivisible, with liberty and justice for all."
The inclusion of the words, "under God" were added first by the Knights of Columbus in 1951, but the official addition didn't happen until June 14, 1954, by a Joint Resolution of Congress. Most likely this addition was to emphasize the difference between the US and the Soviet Union, after all it was the Cold War.
The salute was officially removed in 1942 again by an Act of Congress.
So, Happy Birthday Pledge of Allegiance! Maybe some day we can add "with liberty and justice for all citizens" just to make a point.