This is just fabulous, and I'm tickled to discover Shorpy, I love old photos.
Amazing to note this photo is from a glass negative, not all that uncommon in the early 1900's, before paper-backed emulsions finally took over.
Then as now, the OEM horn on most motorcycles leaves something to be desired ! Notice the hard-tail aft: The leaf-spring you can see alongside the back wheel is for the seat!
119 hours from DC to Frisco would be a pretty good time today, barring you 'Iron-Butt' types.
The text goes on to note that this little trip was part of an exercise to demonstrate the effectiveness of motorcyles as couriers in wartime: The backstory to this was that before WW2, Harleys were an OK motorcycle IF you couldn't afford an Indian. Indian and Harley both were tapped for war production as were most industries then; Harley exploded under the huge wartime revenues they were able to recieve. Indian could not keep pace, lost gov't contracts, and with bad postwar management was gone by the mid-fifties.
Thanks, George !
J o e y