She was the daughter of John Howard Whittemore (1837–1910) and his wife Julia Anna Spencer (1839–1915). Her siblings were Julia Whittemore (1876–1876), John Howard Whittemore Jr (1872–1887) and Harris Whittemore Sr (1864–1927). Gertrude did not marry; she lived with her parents in Naugatuck, New Haven, Connecticut, and travelled widely in Europe.
Among the large collection formed by John Howard Whittemore were several major Whistlers: Symphony in White, No. 1: The White Girl y038, A White Note y044, Green and Grey. Channel y069, and Mother of Pearl and Silver: The Andalusian y378. They were bequeathed in 1910 to the J.H. Whittemore Company, Naugatuck, Connecticut, with life interest to J.H. Whittemore's daughter, Gertrude. In addition she bought Nocturne in Blue and Silver y151 iaround 1911 and passed it to the J.H. Whittemore Company.
'Gertrude B. Whittemore', Alston et al family tree, Ancestry.com.