Mary Ward was born Mary King in Ballylin near present-day Ferbane, County Offaly, on 27 April 1827, the youngest child of the Rev Henry King and his wife Harriette. She and her sisters were educated at home, as were most girls at the time. She was interested in nature from an early age, and by the time she was three years old she was collecting insects. Ward was a keen amateur astronomer, producing sketches of each stage of the process. Along with photographs made by Parson’s wife Mary Rosse, Ward’s sketches were used to aid in the restoration of the telescope.
Ward also drew insects, and the astronomer James South observed her doing so one day. She was using a magnifying glass to see the tiny details, and her drawing so impressed him that he immediately persuaded her father to buy her a microscope. She began to read everything she could find about microscopy and taught herself until she had expert knowledge. She made her own slides from slivers of ivory, and prepared her own specimens. The physicist David Brewster asked her to make his microscope specimens and used her drawings in many of his books and articles.