Born to poor tenant farmers in Telemark, Norway, Ronning as a youth excelled in skiing, tended mountain sheep, and taught school. The local church was strongly influenced by Haugean revivalism. When a new minister remarked that even sons of tenant farmers might receive pastoral training in America (unheard of in Norway) and urged the young man of 2l to go, Ronning packed his bags and entered the Hauge Synod seminary at Redwing, Minnesota. After four years of theological study (1883-1887), during which he tutored classmates in Norwegian and taught in a parochial school, Ronning was called to serve as pastor of a three-point parish near Faribault, Minnesota. A revival broke out in each congregation, accompanied by intense interest in and prayer for missions.
The appearance of two Norwegian China missionaries precipitated the formation of a China Mission Society at the 1890 Hauge Synod convention and caused Ronning himself to hear a "Macedonian call." He and his sister Thea, later joined by Hannah Rorem (who became Ronning's wife), responded to the call, sailed from San Francisco, and arrived in Shanghai in December 1891. A field of service was located in Fancheng, in northwest Hupei (Hubei) Province, with the help of the legendary Griffith John of the London Missionary Society. Here Ronning labored for 15 years (1893-1899, 1901-1908). When his wife died in 1907, he returned to America with his children. At age 46 he embarked on a second pioneering ministry as a frontier missionary in Alberta, Canada.