Peter McEachin was the son of Daniel Malloy and Leah McClellaghan McEachin. He lived all of his life in Florence except while away at school and during World War I. He attended The Citadel from 1912 through 1914 and the University of South Carolina from 1914 to 1916, when his education was interrupted by World War I. During the war, he served in the Ambulance Corps service from 1916–18. After the war, he returned to the University of South Carolina where he studied from 1918 until 1920. He was admitted to the South Carolina Bar in 1920.
He married Margaret Howard in 1924 and their son became a Florence lawyer as had his father.
Elected as a State Senator, he served four terms from 1930 until 1942 and 1946 until 1950. He was a member of the American College of Trial Lawyers, the American, South Carolina and Florence County Bar Associations.
An able trial lawyer, his forté was cross-examination. He was tenacious in representing his clients, yet courteous and cordial in his relationships with opposing attorneys. Adept at keeping disagreeable situations from arising during trials, he also was adroit at developing favorable testimony and minimizing adverse evidence. A forceful speaker, his jury arguments made the most of his clients’ causes.