He was the co-founder and president of Llewellyn Iron Works, a company based in Los Angeles, which provided iron works and steel for the construction of buildings in Southern California, the Western United States, Mexico, and South America.
The company also produced steel from iron ore and during the World War I shipbuilding boom it was one of the largest manufacturers of triple-expansion steam engines on the West Coast.
[9] Llewellyn was a member of the Business Men's Association of Los Angeles, alongside businessmen Walter Newhall, Frank Hicks, John H. Norton, Hancock Banning, Joseph Schoder, James Cuzner, H. E. Graves, and William Lacy.
[11] Llewellyn suffered a stroke on board the Grace Line ocean liner Santa Barbara on her trip between Valparaíso and New York City, where he died in 1936.
[12] His remains are interred, alongside his parents and siblings, in the Forest Lawn Memorial Park (Glendale).