MacDowell was born in Belfast in 1799. His father dies whilst he was young and the family lived in relative poverty.
From 1807 to 1811 he boarded at a school in Belfast, run by an engraver named Gordon, who encouraged his attempts at drawing, and from 1811 to 1813 he was under the tuition of a clergyman in Hampshire. 
Around 1811 he moved with his mother to Hampshire in England, where they had relatives. In 1813, aged 14 (the then standard age to begin apprenticeships), he was apprenticed to a coach-builder in London. However, his master went bankrupt and his training as a coach-builder ended abruptly. During this time he was lodging in the house of Pierre Francois Chenu, the sculptor. It is presumed that this engendered an interest in sculpture within the young MacDowell.
He was elected a Member on 10 February 1846 and presented as his diploma work a "Nymph.".
MacDowell died in London on 9 December 1870.
MacDowell's works include a statue of Sir William Brown in the Great Hall of St George's Hall, Liverpool. His life-size memorial, in marble, to the young Earl of Belfast (died 1853) showing the deceased on his deathbed attended by his mother, was in Belfast Castle Chapel. It was moved to Belfast City Hall.
- W G Strickland, Dictionary of Irish Artists, (1913); Rupert Gunnis, Dictionary of British Sculptors 1660–1851 (1953); Homan Potterton, Irish Church Monuments, 1570-1880 (Belfast 1975).
- Graves 1893.
- Dictionary of British Sculptors, 1660-1851, Rupert Gunnis
- Royal Academy of Arts website
- Sharples, Joseph; Pollard, Richard. Liverpool. In Pollard, Richard; Nikolaus Pevsner (2006). The Buildings of England: Lancashire: Liverpool and the South-West. New Haven & London: Yale University Press. p. 296. ISBN 0-300-10910-5.
This article incorporates text from a publication now in the public domain: Graves, Robert Edmund (1893). "MacDowell, Patrick". In Lee, Sidney. Dictionary of National Biography. 35. London: Smith, Elder & Co.