Des Peres is a city in west St. Louis County, Missouri, United States. The population was 8,373 at the 2010 census. The first inhabitants of De…Des Peres is a city in west St. Louis County, Missouri, United States. The population was 8,373 at the 2010 census. The first inhabitants of Des Peres were the Cahokia, the Kaskaskia, the Mitchigamea, the Moingona, and the Otoe peoples. As well as the Missouria, and Osage, and Tamaroa peoples.