Every county is guaranteed one icon indicating my knowledge and may have a second indicating the signs in use.
The icons are as follows:
- ✔ - Information is certain. I will specify my source within its section.
- ❓ - Information is uncertain. Unless otherwise noted, this is based on observations.
- ✘ - Information is unknown.
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This county uses only the M1-6 (or M1-6M: the Minnesota modification permitting the number to be white) standard style exclusively.
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This county uses the original style M1-X4 sign exclusively.
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This county uses both styles of sign, with the original style being used for some roads and the M1-6(M) style being used for others.