[2] A lifelong Quaker, Simkin was a patient man who spoke with a deep and soft voice, and was described by The New York Times as a peacemaker who "projected a soothing image that fit the part".
"[2] On January 27, 1961, President of the United States John F. Kennedy named Simkin to serve as the fifth Director of the Federal Mediation and Conciliation Service, with The New York Times describing him as "one of the best known arbitrators of labor-management problems in the country".
[3] He was sworn into office on March 31 in a ceremony held at the White House, with United States Secretary of Labor Arthur J. Goldberg remarking on Simkin's status as the first Quaker to hold the post.
He was reappointed by President Lyndon Johnson, and served in the post until 1969, making him the longest-serving director of the Federal Mediation and Conciliation Service.
[2][5] In private practice, Simkin served as an arbitrator assisting major corporations with difficult labor issues at companies including Bethlehem Steel, Goodyear and Greyhound Lines.