Wilkes-Barre's population skyrocketed due to the discovery of anthracite coal in the 19th century. In 1808, Judge Jesse Fell of Wilkes-Barre discovered a solution to ignite anthracite with the usage of an iron grate; it allowed for the coal to light and burn easier. This invention increased the popularity of anthracite as a fuel source. This led to the expansion of the coal industry in Northeastern Pennsylvania; Wilkes-Barre was nicknamed "The Diamond City" due to its high productivity of mining coal. The growing demand for coal as a domestic heat source resulted in changes to patterns of immigration to Wilkes-Barre in the 19th century. The Pennsylvania guide, compiled by the Writers' Program of the Works Progress Administration in 1940, noted that: