The posters were uncovered in Clacton, Essex, earlier this week.
Danny Sloggett, 40, spotted the retro signs in Meredith Road and now wants to ensure they do not end up hidden away again.
"They're relics, they're our history and they show off Clacton's power," Mr Sloggett said.
"The royal family used to come here in the 1920s and 30s. Lots of people used to come from London, and things like this are an important part of our history which has been hidden away."
The posters, which advertised Ambrosia, Black Cat cigarettes and a local cafe, are on the side of a building currently occupied by Sheen's Estate Agents.
An employee there said "loads of people" had come to take pictures over the last few days once the signs had been exposed.
On Facebook, one user said the billboards "should be covered with perspex like the Banksy stuff".
"Should definitely restore it and photograph for a museum," wrote another.
Mr Sloggett said he had not yet contacted Tendring District Council about the possibility of preserving the signs as he wanted to build support for his cause before doing so.
"They're amazing things. I know the history of Clacton but it's nice to see it on display," he said.
The BBC was unable to contact the company that owns the modern billboard.
Advertising billboards thought to be from the 1920s discovered behind a modern hoarding should be preserved "for all to see", a blogger has said.