Are there U.S. states where it is illegal to hitchhike? I have looked around and have not found any site which has substantiated their claims with up to date sources.
It varies from state to state.
Some are legal for it to be done on the shoulder of the road. (green)
Others off the travelled part of the road (eg stand in grass). (yellow)
Others - completely illegal. (red)
Others - unclear. (grey)
Source: DEL CODE § 4147
Source: NRS 484B.297
Note: federal laws supersede state laws, and the federal law states that the legality of hitchhiking within national parks is decided by the superintendent of that park (Source: CFR Title 36 section 4.31).
Credit: All the hard work was done by Hitchwiki, I just compiled all the references in one place.