State Route Marker sign
Marks a numbered highway maintained by the state rather than the federal government.
Federal designation M1-5 in the MUTCD, the national standard every state signs to. The plain square shown here is a stand in for the real thing. Most states design their own outline for this marker, anything from a spade to a keystone to the shape of the state itself.
How to recognise it
This sign is a square in white, the standard background for a rule you must obey. Green for directions, distances and exits. They never tell you what to do, only where things are, which is the simplest way to remember the colour.
What the test wants you to know
The exam rarely asks about the number itself. It asks whether you know a state route can narrow from a divided highway to a single lane county road without warning, so do not assume the same design standards hold along the whole length the way they do on an interstate.
Practise it
Reading about a sign is not the same as recognising it in half a second with an examiner watching. Every state road signs test on this site shows the sign and asks you to name it, then shows four faces and asks you to pick the right one.
Interstate Route Marker
US Route Marker