Born in Tennessee and later trained at A. B. Simpson's Missionary Training Institute, Simpson (no relation to A. B. Simpson) and several other Christian and Missionary Alliance (C&MA) missionaries traveled to China in 1892, hoping to evangelize in Tibet. Identifying with the Pentecostal movement, Simpson left the C&MA in 1916. After two years in the United States, he and his family returned to China in 1918 as Assemblies of God (AG) missionaries. Over the years, Simpson evangelized widely and focused his efforts on the training of Chinese clergy; he remained in China until 1949. In retirement in the United States he continued to promote missions. His son, William EkvalI Simpson, also an AG missionary; died at the hands of bandits on the Tibetan-Chinese border in 1932.