How is the NCT marked?
The NCT is primarily* marked with blue paint blazes on trees / posts and by Carsonite posts that display the official trail emblem and a regulatory strip that defines allowable uses. Side trails are typically marked with white paint blazes. In North Dakota where trees are not as abundant, the NCT is also marked with wooden posts displaying the trail emblem.
Some popular trailhead parking areas and major highway crossings may also have highway signs marking their location while informational, interpretive, and mileage signs are utilized in some areas. See the photos below for examples.
* The Finger Lakes Trail in NY is marked with white paint blazes. Blazes and signs are typically not allowed in designated Wilderness areas.