I found a John Pinkerton who was living on June 5, 1917 in the N____ Hotel, Los Angeles, CA. Born: 1 March 1896, Newry, County Down, Ireland Citizenship: 1917, Alien and citizen of Great Britain Occupation: Milker for Mrs. C. Phelps, Burbank Marital Status: single Signed: J. C. Pinkerton Source: U. S. World War I Draft Registration Cards 1917-18
In 1930 he was living in El Monte, Los Angeles, CA. John Pinkerton, head household, single, b. ireland-North, 33, immigrated 1912, milker dairy.
In 1940 he was living in Los Angeles, Los Angeles, CA. John Pinkerton, b. abt. 1900, North ireland Single Lodger Education: 8th Grade 1935 & 1940: 517 Gladys Avenue, Los Angeles Occupation: Milker dairy farm Citizenship: Naturalized.
I think he's a good possibility. Successful Searching!