Sainte Genevieve County, often abbreviated Ste. Genevieve County (French: Ste-Geneviève), is a county located in the eastern portion of the U.S. state of Missouri. As of the 2010 census, the population was 18,145. The largest city and county seat is Ste. Genevieve. The county was officially organized on October 1, 1812, and is named after the Spanish district once located in the region, after Saint Genevieve, patroness of Paris, France. It includes the earliest settlement west of the Mississippi River outside of New Spain, part of the French colonial mid-Mississippi valley villages.