Dr. P. M. O'Brien was in charge of the Port Townsend Marine Hospital in 1858, having
previously managed a drug store on Water Street. O'Brien apparently sold out his interest
in the hospital after some years
to Dr. George V. Calhoun.
See James G. McCurdy, De Juan de Fuca's Strait: Pioneering Along the Northwestern Edge of the Continent (Portland: Metropolitan Press, 1937). BCDES 26.1.