William Henry Harrison was the eldest son of Joseph Harrison (1810-1874) and Sarah Poulterer Harrison (1817-1906). He had several siblings, Margaret (1839–1923), Alice McNeill (1845–1913), Marie Olga (1847–1848), Theodore Leland (1849–1933), and Clara Elizabeth (1855–1940). His father, Joseph, was a partner in the firm of Eastwick & Harrison, locomotive manufacturers, in Philadelphia, and arrived in Russia early in 1843. The Harrisons knew the Whistlers in St Petersburg; Alice, Marie and Theodore were born in Russia, and William Henry was at school there at the same time as Whistler's brother, William McNeill Whistler (1836-1900).
William Henry Harrison married Mary Rebecca Orne on 29 April 1859, and they had one son, William Henry Harrison jr (1860-1932). The son married Helen Skidmore and had two sons, the diplomat Leland (1883-1951) and Jack.
In 1857 Whistler's mother referred to Harrison senior as a possible patron: 'I hope you mean to practise in your native land your art now being acquired. Both Mr Winans & Harrison are patrons of painting!' (30 April and 4 May [1857], GUW #06472). The family maintained contact with Whistler's family thereafter, but it is not known if they purchased any works by Whistler.
In 1876 William and his wife Mary Harrison visited the Whistlers in London. Whistler's mother, Anna Matilda Whistler, described their visit: 'My Son the Doct reported to me lately, how surprised he was by a call from Mr & Mrs Henry Harrison, with their son of 16 yrs of age! a very fine lad! My Son thought the companion of his boyhood, much improved since they had last met in Phila. ... it was pleasant to Willie to talk over by gone scenes, ... he was invited to join them at their hotel to dine & chat. Jemie was not in his place when they drove to 2 Lindsay [sic] Houses, so they neither saw him or his paintings, tho I hope they may when in London again.' (19 July 1876, GUW #12635).
'William Henry Harrison', Find a Grave website.