Irwin was a Presbyterian missionary who served with the Laos Mission. He was born on 5 September 1859 in Garafraxa, Ontario and graduated from Pardee College, Missouri in 1887. He graduated from McCormick Theological Seminary in 1890 and was ordained by Platte Presbytery in June 1890. He arrived in Bangkok in September of that same year. He married Dr. Mary Alameda Bowman (1864-1954) in July 1898. His ministry with the Laos Mission was marked by controversy because of his faith in the northern Thai churches to lead themselves. In 1894-1895, he played a key role in an attempt to place pastors in most churches, an attempt that led to misunderstanding and reluctance on the part of the Laos Mission to engage in such an experiment again. While stationed at Nan from 1895 to 1900, he developed a plan for new church development that would encourage churches to take responsibility quickly for themselves; that plan came to an end with the mission transferred the new Christian groups involved to the care of other stations. In 1903 to 1905, Irwin prepared the Phrae Church to run its own life without missionary supervision, which it then did until 1912, when the Laos Mission reopened the Phrae Station. The Irwins resigned from missionary work in February 1906, but they returned to Bangkok in 1911 where Irwin was manager of the American Bible Society agency until 1932. He died in December 1943.