Named for Robert de la Salle
Robert de la Salle [1643-1687] was a French explorer. He sailed down the Mississippi River to the Gulf of Mexico and claimed the region for France. He named the area Louisiana after King Louis XIV. De la Salle was responsible for the first European settlements in the area. He and two other French traders built Fort Crevecoeur on the Illinois River near Peoria in 1680, and Fort St. Louis on Starved Rock in 1682. LaSalle was killed by his own men in 1687.
Established in 1831
The northern half of the county had been part of Putnam County, while the southern part was unassigned territory attached to Tazewell County.
The original LaSalle County covered parts of present-day Kendall, Livingston, and Marshall Counties, and the entirety of present-day Grundy County. The current boundaries of LaSalle County were established in 1843.