P.J. Murphy was born in Lanark, Ontario, Canada, on January 23, 1870. His family moved to North Dakota in 1881. Murphy graduated from Grafton High School, and attended the University of North Dakota for a time. He married Mary Ann Normand on July 10, 1901, at Oakwood (Walsh County), North Dakota. The couple had one son, Harold.
P.J Murphy taught at a Catholic School in Oakwood from 1889-1900. In 1900, he became the district manager for the Modern Woodmen of America lodge. He was promoted in 1909 to state manager, a capacity in which he served until his retirement in 1936. He was also a member of the Grafton School Board for eighteen years. Murphy was elected to the North Dakota State Senate as a Republican in 1913, serving until 1933. He was also the first president of the State Board of Higher Education.
P.J. Murphy died January 13, 1942.