In 1951, the Knights of Columbus, the world's largest Catholic fraternal service organization, also began including the words "under God" in the Pledge of Allegiance.[14] In New York City, on April 30, 1951, the Board of Directors of the Knights of Columbus adopted a resolution to amend the text of their Pledge of Allegiance at the opening of each of the meetings of the 800 Fourth Degree Assemblies of the Knights of Columbus by addition of the words "under God" after the words "one nation." Over the next two years, the idea spread throughout Knights of Columbus organizations nationwide. On August 21, 1952, the Supreme Council of the Knights of Columbus at its annual meeting adopted a resolution urging that the change be made universal and copies of this resolution were sent to the President, the Vice President (as Presiding Officer of the Senate) and the Speaker of the House of Representatives. The National Fraternal Congress meeting in Boston on September 24, 1952, adopted a similar resolution upon the recommendation of its president, Supreme Knight Luke E. Hart. Several State Fraternal Congresses acted likewise almost immediately thereafter. This campaign led to several official attempts to prompt Congress to adopt the Knights of Columbus’ policy for the entire nation. These attempts failed.

In 1952, Holger Christian Langmack wrote a letter to President Truman suggesting the inclusion of "under God" in the Pledge of Allegiance. Mr. Langmack was a Danish philosopher and educator who came to the United States in 1911. He was one of the originators of the Prayer Breakfast and a religious leader in Washington, D.C. President Truman met with him along with several others to discuss the inclusion of "under God" and also "love" just before "liberty and justice".[citation needed]

At the suggestion of a correspondent, Representative Louis C. Rabaut of Michigan sponsored a resolution to add the words "under God" to the Pledge in 1953.