Agnes Mary ('May') Alexander was the eldest daughter of the banker and collector W. C. Alexander and Rachel Agnes Lucas. She had three brothers and five sisters. The family lived at Aubrey House in Kensington, London.
May trained as a nurse at University College Hospital in London and became interested in housing and social issues. She wrote Some Kensington Problems in 1904 and was a Guardian of the Poor for Kensington. She was also a collector.
As a young girl May posed for JW. According to W. C. Alexander, he commissioned JW to paint his daughters in 1872 because he admired Arrangement in Grey and Black: Portrait of the Painter's Mother (YMSM 101). May's portrait, Miss May Alexander (YMSM 127), was executed in the diningroom of the family's home, for which JW designed a decorative scheme. It was in this room that the portrait was intended to hang. The Alexanders proposed that May should pose in riding habit and JW suggested that she wear a picture hat (#07583). However, JW postponed sittings until he had finished the portrait of Agnes' sister Cicely, Harmony in Grey and Green: Miss Cicely Alexander (YMSM 129) (#07572). In 1875 May's portrait was taken up again but there was further delay due to her ill health. Her sister Grace was also posed for JW (see Miss May Alexander (YMSM 127) and Portrait of Miss Grace Alexander (YMSM 130)). W. C. Alexander acquired a group of pen drawings which included portraits of Cicely (Design for a dress for Miss Cicely H. Alexander (M.503)), May (Study for 'Portrait of Miss May Alexander' (M.498) and Study for 'Portrait of Miss May Alexander' (M.499)) and Grace (Sketch for 'Portrait of Miss Grace Alexander' (M.506) and Sketch for 'Portrait of Miss Grace Alexander' (M.507)).
Pennell, Elizabeth Robins, and Joseph Pennell, The Life of James McNeill Whistler, 2 vols, London and Philadelphia, 1908; Young, Andrew McLaren, Margaret F. MacDonald, Robin Spencer and Hamish Miles, The Paintings of James McNeill Whistler, New Haven and London, 1980; MacDonald, Margaret F., James McNeill Whistler. Drawings, Pastels and Watercolours. A Catalogue Raisonné, New Haven and London, 1995.