The Splügen route (but also the Julier, Septimer and San Bernardino) with access through the Rhine Valley, has been an important and lucrative transport route since Roman times. It is to this location that St. Margrethen owes its Roman origins and later its medieval castles (Grimmenstein castle on a steeply sloping rock spur with views of the Rhine Valley and Bodensee).

St. Margrethen with its border crossing and railway station is an important traffic hub (e.g. direct trains to Munich). There are various flight connections from nearby Altenrhein. The convenient location near the border has given the town its character, for example with its shopping centre which attracts visitors from over the Swiss border. In earlier days the area where the Rhine enters the Bodensee was often flooded. The Rhine correction completed at Fussach in 1900 brought relief and with the «Alter Rhein», has in the meantime been upgraded to a near-to-nature recreational area with a gently-flowing river. Today, the Bruggerhorn area on the Alter Rhein is a nearby recreational spot for St. Margrethen, with a lovely lido, camping site and tennis courts. Also worthy of note is the Eselschwanz nature reserve offering walkers and joggers wonderful paths alongside the river. Relaxation is on offer at the mineral health spa with its bathing and therapy options, saunas and solariums.

In recent years, the mild climate has boosted wine production in the St. Gallen Rhine Valley. The flat valley floor is also ideal for cyclists and skaters. And between St. Margrethen and Au, the Heldsberg fortress museum is a reminder of the threat faced during the 2nd World War.