Rivera was born in Penuelas, Puerto Rico, where his father and four uncles were Episcopal Priests. In 1944, he graduated from the Church Divinity School of the Pacific in Berkeley, California, and was ordained to the priesthood. From 1943 to 1944 he was vicar of Grace Church in Martinez, California, and from 1945 to 1968, he was rector of St. Paul's Episcopal Church, Visalia, California. He also held diocesan offices in the Diocese of San Joaquin.