Ancestors of Firmin Desloge, the city's founder, migrated from France and settled in Potosi.  There he became acquainted with mining through his father and acquired numerous claims in modern day Desloge and Bonne Terre.  Desloge developed one of his claims just north of Bonne Terre and built a concentrating plant there.

The plant was destroyed by fire in 1883 and rather than rebuild, Firmin Desloge decided to explore his properties in the present area of Desloge.  In 1887, the land was cleared and company houses for his staff were constructed in an area referred to as "Desloge Town", just west of the present day railroad tracks.  Here, Desloge sunk a shaft and built a concentrating plant which commenced operations in 1892.   The plant ran under his operation until 1929 when it was sold to the St. Joe Lead Company.

Firmin Desloge moved to St. Louis in the early 1900's, and his grandson William remained until 1921, when he too moved to St. Louis.