Complex sentence: Upon first arriving in the region, Steele could not convince any of his clients to try his progressive designs, but beginning with his Prairie-influenced Ben and Harriet Schulein House (Sioux City, 1913), Steele began tentatively moving in the Prairie School direction.
Split into simpler sentences: Upon first arriving in the region, Steele had been unable to convince any of his clients to try his progressive designs. However, beginning with his Prairie-influenced Ben and Harriet Schulein House (Sioux City, 1913), he had began tentatively moving in the Prairie School direction.