Thomas H. Keown was born in Ireland c. 1814
Thomas Heron Keown of Down, Ireland was included on the list of gentlemen to whom the Court of Examiners granted Certificates of Qualifications (Apothecaries' Hall) in 1836. 
In an 1836 edition of the London Medical Gazette
, Thomas H. Keown is on the College of Surgeons List of Gentlemen who received Diplomas the previous August.
Until 1838 he was employed as Assistant Surgeon on the Britannia
. He was appointed to the position of Hospital Mate at Haslar in February1838.
In October 1841 - March 1842 while appointed to the Pantaloon
was promoted to the rank of Surgeon. He was appointed to the Snake
in the same year. 
In 1845 he was appointed to the Vesuvius
. Class C. which was serving in North America and West Indies.
In 1847 he was appointed to the Royal Marine Detachment at Port Essington
In 1853 he was appointed to the Winchester
, 50, flag ship of Rear-Admiral Hon. Sir F. B.R. Pellew, C.B. on the East Indian station.
In 25 April 1859 he was appointed to the Cressy
, 80. Screw Steam Ship, 400 horse power in the Mediterranean.
Surgeon Superintendent Convict Ships
Thomas H. Keown was employed as Surgeon Superintendent on two convict ship voyages to Australia:
1). Mount Stewart Elphinstone
- arrived in Van Diemen's Land from London and Gibraltar with male convicts on 18 May 1848. He returned to London on the City of Poonah in July 1848.
2). Hyderabad to Van Diemen's Land in 1850.
Thomas Heron Keown, age 43, married Eliza Harrison on 13 Aug 1857 at Drumbeg , Down, Ireland (marriage recorded for potential Royal Navy widow's pension) (National Archives)
He is listed in the Medical Registry 1865 - Qualifications Mem. Royal College Surgeons, Eng. 1835. Lic. K.Q. College Physician Ireland 1862.
Thomas Heron Keown died on 9 December 1876 at Sydenham, Belfast, Ireland.
 The Standard 24 June 1836
 London Medical Gazette
 Hampshire Telegraph 19 February 1838
 Medical Times October 1841 - March 1842
 Medical Times