Then he received an unexpected letter. The return address said "Box B, Salt Lake City, Utah." As every Mormon of that and several later generations knew, such a letter was Manwaring's call to go on a mission for the church. He was granted six months to work and save enough to pay his mission expenses. Manwaring left Utah in February 1899. After three weeks in Sydney, Australia, he spent his mission years in Tasmania. He returned to Utah in March 1903.