He also attended a New Jersey Constitutional Convention, hosted a long-running radio commentary show, and was a prolific writer of letters to the editor of major newspapers.

Phelps served in the United States Army during World War II, achieving the rank of Captain.

The United States Navy largely withdrew from the island with the last naval governor, leaving Phelps to restructure an economy previously centered on the military.

There, he had to negotiate land sales between the two governments and respond to citizen's anger when possible assassinations on United States soil were ordered by Trujillo.

[2] During World War II, Phelps served in the reserve corps until enlisting in the United States Army in 1942.

[3] In 1928, he ran for a nomination for the United States House of Representatives, but lost the primary to Ruth Baker Pratt, who would become the first congresswoman from New York.

[2] After leaving his diplomatic post in the Dominican Republic, Phelps served as commissioner for the Palisades Interstate Park Commission.

Phelps immediately needed to address the failing economy of American Samoa, caused largely by the withdrawal of the United States Navy from the islands with the final naval governor.

[2] Phelps criticized the United States military for refusing to build recruitment centers in American Samoa, leaving natives who wanted to enlist the need to travel to Hawaii to do so.

[6] Only days after leaving the governor's seat, Phelps received appointment as the United States Ambassador to the Dominican Republic, serving from June 27, 1952, to May 30, 1953.

Among the issues he faced were accusations of numerous murders of Americans on United States soil ordered and funded by Trujillo.

Phelps received much of the attention of his mother and grandmother during his childhood; this led to a strained relationship with his sister, who remained embittered towards him for the rest of her life.