Saint Louis University (SLU, /ˈsluː/) is a private Roman Catholic four-year research university with campuses in St. Louis, Missouri, United States and Madrid, Spain. Founded in 1818 by the Most Reverend Louis Guillaume Valentin Dubourg, It is the oldest university west of the Mississippi River and the second-oldest Jesuit university in the United States. It is one of 28 member institutions of the Association of Jesuit Colleges and Universities. The university is accredited by the North Central Association of Colleges and Secondary Schools. SLU's athletic teams compete in NCAA's Division I and are a member of the Atlantic 10 Conference. It has an enrollment of 13,505 students, including 8,687 undergraduate students and 4,818 graduate students that represents all 50 states and more than 70 foreign countries. Its average class size is 23.8 and the student-faculty ratio is 12:1.