Wikipedia Born in Canada, Carscallen grew up in North Dakota, where he was baptized at age 20, just prior to starting studies at Union College from 1900 to 1901. He completed his Seventh-day Adventist (SDA) ministerial training in September 1906 at Duncombe Hall Training College in England. That same year, following his ordination, he embarked for Kenya, East Africa, to begin missionary service for the SDA as superintendent of the British East Africa Mission, together with Peter Nyambo, an African Adventist worker from Nyasaland, now Malawi, who was a classmate of Carscallen at Duncombe Hall. 

The first SDA missionaries to work in Kenya were Arthur Carscallen and Nyasaland native Peter Nyambo. Leaving England, the two traveled to Hamburg, Germany, sailing from there on 1 October 1906 to East Africa. Describing the journey to Africa, Carscallen wrote. "After an exceedingly hot trip through the Red Sea, we arrived in Mombasa nearly three weeks later.'

By November 27, 1906, Carscallen and Nyambo were able to open the first British East Africa Mission station in Kenya at Gendia Hill near the eastern shore of Lake Victoria on Kendu Bay with the assistance of Abraham C. Enns, a German missionary and gardener stationed in Tanganyika, today Tanzania. Enns had arrived in Tanganyika in 1903 and was working among the Pare people. Together, they chose a five-acre plot, about three kilometers (two miles) inland from Kendu Bay for the mission site, which was situated among the Luo people in what is now South Nyanza, about which Carscallen says, "... we chose the site at Gendia among the primitive African tribe who spoke a Nilotic language." Carscallen and Nyambo worked quickly to construct the mission buildings. Nyambo remained at Gendia for about four years.^[3]Within 14 months Carscallen reported that he and Nyambo had erected the basic mission buildings and that he had learned the Luo language. As superintendent of the Mission, Carscallen and his staff established missionary stations along the eastern shore of Lake Victoria at Gendia Hill, Wire Hill, Rusinga Island, Kanyadoto, Karung, Kisii (Nyanchwa), and Kamagambo. The first 10 Jaluo Adventist adherents in Kenya were baptized on 21 May 1911.Publishing was central to the mission of the early Adventist Church. Thus, in 1913, Carscallen acquired a small press for the Mission during a trip home to the United States and returned to set up African Herald Publishing at Gendia in order to publish books, papers, and a monthly journal. Carscallen was one of dozens of church leaders who helped expand their faith worldwide through publishing ministries. (more)
Ancestry Passenger list In 1921  Helen b. 1881 and Harry b. 1908 and George b. 1913. In North Dakota Census 1925 his wife is Anita
The second wife and children above come from Ancestry Passenger List 1941
Missionary at Gendia Mission near Kendu in 1911, with his charming Scotch wife and a bright curly-headed boy of three summers. Gethin - Missionary of the S.D.A. Mission. Not much interested in converting, more in trading.
Medals - East African Intelligence Department - Arthur A. Carscallen, Agent
Red Book 1912 - A.A. Carscallon - Kisumu
Red Book 1912 - Seventh Day Adventist Mission, Kendu

Red Book 1919 - District Committees - Kisii - A. Carscallen

Red Book 1919 - Seventh Day Adventist Mission - The Mission is of American nationality and was established in November 1906 in the Nyanza Province where there are 7 stations. The object of the Mission on entering the field were to start industrial work in connection with education. Being situated in a Reserve, however, where little land can be secured, the Mission had to resort chiefly to book education. Chief of the Mission - A.A. Cascallen [sic], Kamagambo Mission, Kisumu

Gethin - 'I had not been in Kisii long when two people came to see me. They were both Missionaries and claimed  ownership to a religion I had never heard of before. They introduced themselves as Pastor Sparks and Pastor Cascallon of the S.D.A. Mission, which they informed me followed the Old Testament and kept Sunday on a Saturday. As far as I could see they were not very religious and were far more interested in trading buffalo hides for which they got five cows per hide from the Jaluo than they were in converting the native to their way of thinking. I went on a most interesting safari with them which lasted about a week. They were going to spread the Gospel while I was to help them shoot elephant or any other big game that got in the way. We started from Kisii before daylight one morning and made our way to Kanyandoto and Kanyankala where we cut across to the Migori and Kuja Rivers. When we got to Kanyankala we came to an S.D.A. Mission house which appeared to be nothing more than a large store which was full of buffalo hides and trade goods. Preaching of the Gospel was conspicuous by its absence. Cascallon would see an old Jeluo native asleep in the shade of a tree. He would approach him and put his hand on his head. If he still slept he gave him a kick on the backside and say, "Son, you are saved and you can thank the Lord it is me who has saved you, if it was one of the others you would be condemned to terrible torture when you died". With this the convert would be roped in to carry a load on the next safari. Sparks was a keen trader and a good shot. We had no difficulty in getting two good tuskers and we returned to Kamagambo where they had a Mission, via Kadem and Suna. Cascallon was a Canadian and Sparks a South African. Cascallon tried to ape the Cockney accent and Sparks the American, so it gave one a bit of a headache when they were both talking at the same time. Sparks would talk Luo like a native ...........' (more p. 41)

Red Book 1919 - A A Cascallen - Mission - Kisumu

https://encyclopedia.adventist.org/article?id=DJAN In November 1906, Arthur A. Carscallen founded the Gendia Mission. Carscallen (locally known as “Bw. Kaskal”) came to Kenya through the Port of Tanga in Tanganyika (German East Africa) together with Peter Nyambo. They moved from Tanganyika to Lake Victoria and then to Kendu Bay which was under the jurisdiction of Chief Ougo Apela. Chief Ougo took them to Gendia where he could see Kisumu at a distance. He later started looking for other areas and, in 1909, he opened Wire Hill as their second station. He then moved to open Gem as the third station in 1910 then Karungu came in 1912 as the fourth station. The fifth station was Rusinga on the island in 1912 followed by Nyanchwa as the sixth station that same year. In 1913, Kanyadoto (Rapedhi) was founded as the seventh mission station.