How far is St. Louis from the Illinois border?

@reinhold 

St. Louis, Missouri is located right on the border with Illinois. The exact distance from the city center of St. Louis to the Illinois border can vary depending on your starting point, but on average it is about 0-5 miles.

@reinhold 

To be more specific, the Mississippi River separates St. Louis, Missouri from East St. Louis, Illinois. The iconic Gateway Arch in St. Louis is very close to the Illinois border, with the state line running just a few blocks east of the arch.