Complex sentence: In 1680, René-Robert Cavelier, Sieur de La Salle built the first fort in Illinois, Ft. St. Louis, at Starved Rock and later relocated to the present site of Creve Coeur, near Peoria, where the Jesuits relocated.
Split into simpler sentences: In 1680, René-Robert Cavelier, Sieur de La Salle built the first fort in Illinois, Ft. St. Louis, at Starved Rock. Later it was relocated to the present site of Creve Coeur, near Peoria, where the Jesuits relocated.