History says the earl, John Montagu, first ordered a sandwich in 1762 while playing cards with his friends. He asked for beef between two slices of bread so he could still easily eat while playing.
Sam Bompas, a so-called foodsmith, said Montagu probably wasn't the first to think of the idea.
"Other people were probably eating in that way anyway but they were people who weren't written about," he said.
It's possible the sandwich could have been named something else entirely. The first earl of Sandwich had the opportunity to choose Portsmouth instead of Sandwich when he was offered a peerage in 1660, said Steve Laslett, one of the organizers of the Sandwich Celebration Festival taking place Saturday and Sunday.
"Today we could be eating a Portsmouth," he said.
During the celebration, the east Kent town will have sandwich-making competitions and re-enactments of the earl requesting his namesake, the BBC reported Saturday.
The 11th earl of Sandwich, also named John Montagu, is scheduled to host a lunch Sunday.
"I am delighted to wish a happy 250th birthday to the sandwich," he said.