Bellamy crafted it as a resonating oration to bolster the idea that the middle class could fashion a planned political and social economy, equitable for all, Baer said.
After a proclamation by President Benjamin Harrison, the pledge was first used in public schools on Oct. 12, 1892 during Columbus Day observances.
The original wording was: "I pledge allegiance to my flag and to the Republic for which it stands: one nation, indivisible, with liberty and justice for all."
There were those who claimed The Youth's Companion editor James B. Upham penned the famous pledge, but the U.S. Flag Association ruled in 1939 to recognize Bellamy was the author.
The pledge has been changed a few times since. For Flag Day in 1924, "the flag of the United States of America" was officially adopted as a substitution for the phrase "my flag."
In 1954, the words "under God" were added, after a campaign by the Knights of Columbus, a Catholic men's service organization, and other religious leaders who sermonized that the pledge needed to be distinguished from similar orations used by "godless communists."
The prospect of atomic war between world superpowers so moved President Dwight D. Eisenhower that he directed Congress to add the two small but controversial words.
"From this day forward, the millions of our school children will daily proclaim in every city and town, every village and every rural school house, the dedication of our nation and our people to the Almighty," Eisenhower wrote at the time.
In 1988, the elder George Bush made the pledge a presidential campaign issue after Massachusetts Gov. Michael Dukakis vetoed a bill requiring teachers to recite the pledge. Some Republicans sought to require a recital in Congress, but House Speaker Jim Wright, D-Texas, soon casually and voluntarily started a morning recital.
The Senate began reciting the Pledge on June 24, 1999, after passing a resolution at the urging of Sen. Bob Smith, R-N.H.
There is some protocol when reciting the Pledge of Allegiance. Uniformed military personnel face the flag and give the military salute. Civilians stand at attention or place the right hand over the heart. Men traditionally remove their hats.
Baer, author of "The Pledge of Allegiance: A Centennial History," said more modifications can be expected.
"It's about time for another change to take place in the pledge. It's a living document," Baer said.