It's a popup on their site and I can't link to it.

History of the PoA.

1892:
The pledge, written by socialist editor and clergyman Francis Bellamy, debuts September 8 in the juvenile periodical The Youth's Companion. He wants the words to reflect the views of his cousin, Edward Bellamy, author of "Looking Backward" and other socialist utopian novels. It reads: "I pledge allegiance to my Flag and the Republic for which it stands; one nation indivisible, with liberty and Justice for all."

1924:
The words "the flag of the United States of America" are substituted for "my Flag." Fittingly, the change takes place on Flag Day.

1942:
The government officially recognizes the Pledge of Allegiance.

1954:
Worried that orations used by "godless communists" sound similar to the Pledge of Allegiance, religious leaders lobby lawmakers to insert the words "under God" into the pledge. President Dwight D. Eisenhower, fearing an atomic war between the U.S. and the Soviet Union, joins the chorus to put God into the pledge. Congress does what he asks, and the revised pledge reads: "I pledge allegiance to the flag of the United States of America and to the Republic for which it stands, one nation under God, indivisible, with liberty and justice for all."