What's the lowest number that isn't used as a state highway number?

[KCRoadFan]

This just came to mind: of all the numbers that are used for state highways, what's the lowest one that doesn't appear? It seems like all the 3-digit numbers are covered, helped along by states such as Florida and Pennsylvania. Meanwhile, Kentucky, Louisiana, and the FM roads in Texas have many 4-digit numbers among them that run well into the 3000's - but I'm sure that that trio of states doesn't include every single possible number in that range. Going through those highway numbers, what is the first one that doesn't appear in any state?

(I'm pretty sure this thread was already made years ago, although I could be mistaken.)

[formulanone]

The general consensus is "1928", for routes with a reassurance shield.

North Carolina uses it various places as a state secondary route, and there might be a Virginia Secondary route with the same number. There might be a reference or quadrant route (Pennsylvania) with the number. But Kentucky decommissioned it a few years ago, and Texas dropped it from the FM/RM ranks several decades back. No other states seem to post that number. I found a county route shield with the number, but that seems to be it.

Currently, we're stuck in 2704 in the 1-2-3 game, but we accept Route numbers from anywhere in the world for that game.

[SEWIGuy]

There is no highway "0" (zero) that I am aware of in the United States, though there are in other countries.

[KCRoadFan]

There is no highway "0" (zero) that I am aware of in the United States, though there are in other countries.

Forgot about that. I meant starting from 1 upwards - that is, not including zero.

[SEWIGuy]

There is no highway "0" (zero) that I am aware of in the United States, though there are in other countries.

Forgot about that. I meant starting from 1 upwards - that is, not including zero.

Also assuming you mean integers only!