Principia is located on two campuses 50 miles apart from each other in the St. Louis, Missouri, area of the midwestern United States. By plane, St. Louis' Lambert International Airport is almost equidistant between the campuses.

Principia College is in Elsah, Illinois, 12 miles north of Alton, Illinois, on the Great River Road, Route 100. Turn right at Elsah Road, bearing right to Mill Street. Go halfway through the village of Elsah to the first stop sign. Turn right and go up the hill to the main entrance of the college.

For directions from wherever you are to the College, go to Mapquest and click on the Get Directions link (above and to the right of the map). If you use GPS in your car, these are the coordinates for the gatehouse — Latitude: 38.9555, Longitude: -90.3475

The St. Louis campus — including the Pre-School through Upper School, as well as the Acorn program for babies and toddlers, and the business office for The Principia — is located at 13201 Clayton Road in west St. Louis County, near the intersections of Interstate 270 and Highway 40 (I-64). Take the Mason Road exit south off Highway 40, go .8 mile to Clayton Road, turn left and go another .8 mile to the main entrance of the campus.

For directions from wherever you are to the St. Louis Campus, go to Mapquest and click on the Get Directions link (above and to the right of the map). If you use GPS in your car, these are the coordinates for the front gate — Latitude: 38.6267, Longitude: -90.4689
For more information about how to get to Principia, call 800-218-7746 for the St. Louis campus or 800-277-4648 for the College campus in Elsah, Illinois.