[toomuchtodo]

Billboards are illegal in Vermont, Alaska, Hawaii, and Maine.

[jonhohle]

I wondered how they got around the first amendment - here's more info on that (not specific to those states) - http://www.firstamendmentcenter.org/billboards

[copsarebastards]

Did you read the page you linked?

The supreme court ruled that billboard bans based on location (for city and land planning purposes) would be appropriate, but billboard bans which determined which kinds of content were appropriate for public discourse were unconstitutional. A blanket ban across the state is constitutional, but a ban which targets certain kinds of content is not.