Francis Guthrie conjectures the four color theorem at University College London

Background. Francis Guthrie, a mathematician who obtained his LL.B. in 1852, posed the Four Colour Problem in 1852. While attempting to color the map of counties of England, he observed that only four colors were necessary to distinguish adjacent regions. This observation formed the basis of the conjecture, which later became a famous unsolved problem in graph theory.

Communication to De Morgan. Guthrie inquired about the problem with his brother Frederick, who subsequently took the question to Augustus De Morgan. De Morgan recorded the inquiry, noting that Francis Guthrie had posed the question. The conjecture was later published in The Athenaeum in 1854 by 'F.G.' and again by De Morgan in 1860, establishing the historical record of the conjecture's origin.

Legacy and Resolution. The four color theorem resisted proof for over a century. Although the five color theorem was proven in the 1800s, the four color theorem was not proven until 1976 by Kenneth Appel and Wolfgang Haken using a computer-aided proof. Early attempts by Kempe and Tait were shown to be incorrect in the 1890s.