Joseph Frank Piani was born near Milan, Italy, on October 15, 1880. He graduated from the University of Torino and served the Italian government as a superintendent of schools until leaving for Brazil in 1902. While teaching college in Recife, Brazil, Piani became a Christian and adopted the Baptist faith. In 1906, Piani came to the United States to study English at William Jewell College in Liberty, Missouri. It was then that he anglicized his name to Plainfield.
In 1911, Plainfield graduated from Southern Baptist Theological Seminary with a Doctor of Theology. After his marriage to Alice Josephine Lucas in 1912, he returned to Brazil as a missionary pastor and teacher at the Rio Baptist College and Seminary. The Plainfields returned to the U.S. in 1915 to work for the Home Mission Board among Italians and other immigrant groups in Barre, Vermont. From 1917 to 1946, he held a succession of pastorates in Newark, St. Louis, and Tampa. Upon retirement in 1946, the Plainfields moved to Lakemont Colony, SC, where they lived until Mrs. Plainfield’s death on January 22, 1969. Joseph Plainfield spent the rest of his life in Travelers Rest and Tigerville. In retirement, he served as interim pastor at Poe Mill, Sans Souci, and Ebenezer, and taught Sunday School at Travelers Rest First Baptist Church. He died on September 27, 1976.