William Archer was born on 6 May 1830 in
Maghera hamlet, County Down. He was the eldest son of the Reverend Richard Archer (d. 1849) and Jane Matilda (Campbell) (d. 1866). William Frazier, Archer's colleague at the National Library of Ireland, wrote in Archer’s obituary that he was the "eldest son". Frazier’s obituary also mentions Archer’s "only brother, Holt Waring Archer". However, various sources cite two younger brothers: Holt Waring Archer and Richard Henry Verling (H.V.) Archer, and one sister, Matilda Jane Humphreys (Archer). Sources differ on Archer’s exact siblings and their birth order, often mentioning the other siblings but not William. Swanzy's entry for Rev. Richard Archer describes second son Holt, third son Richard H.V., and a daughter Jane, but there is no mention of William Archer listed as first son. Archer's father was born in Wexford and was ordained a
curate in 1823. Archer's parents were married in Dublin in 1825, the same year that Rev. Archer graduated from university at
Trinity College, Dublin. Rev. Archer was the Primary Curate of Maghera hamlet from 1825 to 1835, going on to become the primary curate of
Clonduff. Both of Archer's brothers predeceased him: Richard H.V. Archer died in 1863 and Holt Waring Archer died in 1883. His sister, Matilda Jane, married Dr. Hutchinson D. Humphreys in 1852. His mother Jane died in Dublin in 1866. His paternal grandparents were William and Mary Archer. Archer’s great-uncle on his maternal side, the Reverend Holt Waring, was the Dean of Dromore. His maternal grandfather was Watkins William Verling from Dublin. His brother Richard was a Barrister in a landed estates court in
Cavan. Archer moved to Dublin around 1849, where he helped found the Dublin Microscopical Society and became involved in pursuits of scientific study and librarianship which would define his life and career, spending "his early life…unselfishly devoted to scientific research by which he secured a widespread reputation little understood beyond the abstract world of science." == Career and role in librarianship ==