 He rose to prominence as physician, educator, real estate developer, and newspaper editor in Sacramento, becoming part of the social circle of early California notables such as Leland Stanford, Charles Crocker, Collis Huntington, and Mark Hopkins.Harkness was a participant in the ceremony marking the completion of the First Transcontinental Railroad, representing California and bearing the Golden Spike that was driven by Leland Stanford marking the completion of the railroad.Having earned a large fortune in Sacramento real estate, Harkness retired his medical practice in 1869 and relocated to San Francisco.