Honestly, there is no way that this question could be answered in short. Each state will have different laws and regulations so if you want to be sure, check out your specific jurisdiction. However, let’s take California as an example. Their legislation states that a fixed blade can be carried openly. What they mean by “open” is with a sheath that is worn in plain view. Perhaps, suspended from your waist. When you decide to conceal a dirk or dagger, which is defined as an instrument with or without a handguard that is capable of inflicting great injury or death, it is illegal and you will get punished.
This is just for California so, again, this could vary depending on the state you live in. Be sure to get confirmation from your state’s regulation guide.