Oscar Sigfrid Earlson was born in Folkenberg, Sweden on October 19, 1886 and immigrated to the US in May 1906 arriving in New York City. He arrived in Portland on February 14, 1910 and was married here to Tekla Bergh, also a Swedish immigrant, on April 19, 1910. The couple raised two sons, Rudolph (also a home builder) and Bertel, a machinist. In 1941, Earlson was living with his family at 104 NE 66^th Avenue.

Earlson was active in Swedish cultural life in Portland. In 1936 he was elected district master of the Pacific Northwest Division of the Swedish Order of Vasa. In 1940, he was elected president of the United Swedish Societies and frequently presided over Swedish cultural, music and dance events.

Earlson worked with well-known Portland residential architects like Roscoe Hemenway and Ewald Theodore Pape and built many homes and commercial buildings between 1926-1950, including the following: 3615 East Burnside (1926); 427 NE 67^th (1926); 3005 SE Carlton (1927): 104 NE 67^th (1927); 2526 NE Ainsworth (1931); 2051 SE Division (1932); 6430 SW Parkhill (1938); 2909 NE Ainsworth (1938); 2135 NW 29^th (1944); 2605 SW Talbot (1950).

In 1932, Earlson became a partner and the general contractor for construction of the Mayfair Greens and Fairway, a 12.5 acre driving range, putting course and clubhouse that existed at the northwest corner of SE 82^nd and Division, which today is the Southeast Center Campus of Portland Community College.

Oscar and Tekla lived in Oak Grove in the 1950s and later moved to Seaside, where he died on October 20, 1961 at age 75.