why do some interstate signs have the State on them while others do not?

Question

Is there a reasonn for this or is it a preference?

Answer 1

It depends on the state - in California, for example, Interstate trailblazers or reassurance signs (the red, white and blue shields you see posted independently on the side of the road, usually after an interchange or junction - they're designed to remind you of which road you're on) contain the state name just beneath the word "INTERSTATE," within the blue field of the shield. This was the old standard - the new MUTCD calls for trailblazers and reassurance signs to carry only the number in the blue field, usually much larger than the numbers were previously.

Various states have various kinds of state route signs, most of which (but not all) contain the state name or some unique identifying characteristic - the state route shield for Colorado, for example, has the same "C" logo as the state flag. The Nevada state highway shield is a black square with a white stylized map of Nevada emblazoned in the center, and the word "Nevada" written across the southern third of the state outline. Some are truly boring - a white circle in a black square with no other identifying marks - interchangeability was apparently someone's goal in those states.

Back to interstates, though - the older the sign, the more likely it is to have the state name across the top beneath the "INTERSTATE" banner. This tends to occur most often in Western states, but does appear on the East Coast, too (the Washington D.C. ones are particularly odd - "D.C." only; guess the full name wouldn't fit!). If you should happen to see a US route sign (a white shield) with a state name, you've found a treasure - those were no longer produced after the mid-1960s (unless, of course, it's a reproduction or special marker).

Answer 2

Those are state highways. The interstates just have a red white & blue shield. Sometimes they merge for a stretch so you'll see both.

Answer 3

Only the "Blue Shield" highways are Interstates. The ones you saw with "State" in it are likely State highways.

Answer 4

Well I stole the new mexico sign on the way up from texas that partly helps answer your question I guess.

Answer 5

each state does their own thing.