PORTLAND – It all started with Giovanni Amato selling his freshly baked bread to Italian immigrants laying stones and working on the docks in 1902. Then he added cheese. A little salami. Some vegetables.

Thus was born the Italian sandwich, a humble concoction with oil, salt and pepper that remains a local favorite 100 years later.

Call it Portland’s contribution in a world of hoagies, heroes, grinders, Dagwoods, submarines, cheese steaks and po’ boys.

“You really have to try them to get addicted to them,” said Dominic Reali, who owns the Portland-based Amato’s Sandwich Shop chain. “It’s a great meal. They’ve survived because they were very affordable.”

Amato’s Italian, which features meat, cheese, tomatoes, green peppers, spicy pickles, black olives, onions and oil on freshly baked bread, was the inspiration for one of the founders of the Subway chain.

Unlike Subway, which has 17,400 restaurants in 75 countries, Amato’s kept close to its Portland roots, with 14 locations in Maine.

Others may lay claim to inventing the Italian, but Reali contends it was Amato, an Italian immigrant, who created it by happenstance as he began selling sandwiches from a pushcart after he opened a bakery in 1902.

Nobody knows the precise date of the first Italian sandwich, but Amato’s sandwich historians say it had happened by 1903.

It was a time around the turn of the century in which Italians were coming to New England in large numbers to lay paving stones on streets, extend railway lines and work as longshoremen on the waterfront.

By the 1920s, Amato had opened a sandwich shop on India Street. In the 1950s, people would line up outside the shop to get their Italians, and Amato’s would sell 5,000 sandwiches on Sundays, Reali said.

The rest is history. There now are dozens of imitators selling Italian sandwiches in Maine’s largest city.

People love them so much that there was a panic last spring when longtime bakery Nappi’s closed, forcing sandwich shops to scramble for buns to keep their customers supplied with Italians.

Order one in Portland, and other parts of New England, and the folks behind the counter will know what you’re talking about. But beware, people in other parts of the country might be bewildered, or even provoked.

“You better be careful. People might take offense,” said Herb Adams, a former state lawmaker and Portland’s unofficial historian, who was counseled in a New York deli not to call them Italians.

In New York, similar sandwiches are called heroes or subs. In Boston, they’re often called grinders. In Philadelphia and New Jersey, they’re called hoagies. In the South, they have poor boys, or po’ boys.

The Italian is similar in appearance to some of those sandwiches, but Italian devotees say there are subtle differences.

Unlike most sandwiches, the Italian doesn’t have lettuce. Neither does it have mayo or mustard. Instead, it’s topped with salt and pepper, and a squirt of oil. The freshly baked buns are soft, not crunchy, and filled with veggies aplenty. The meat is ham or salami. The cheese, ironically, is American.

The combination seems to work. Reali describes it as a “crunchy, tangy, sweet mixture of texture and flavor.”

“I can’t tell you why, but they’re good. There’s just something about them,” Jon Knowles of Cumberland, a lifelong Amato’s customer, said last week as he left Amato’s with an Italian under his arm.

“It’s easy. It’s fast. And it’s cheap,” said Kerry Strout of Portland as she grabbed an Italian for lunch.

It’s also a bit messy. The oil on the traditional Italian makes the sandwich a challenge to eat.

Roger Hutchins of Portland joked that the oily sandwich serves to keep the hands soft during harsh Maine winters.

“It keeps your hands from getting dried out. If the oil is not dripping off, it’s not quite the same,” he said.

Amato’s still has a shop on India Street, in a neighborhood known as Little Italy, which is home to Micucci’s Grocery Co., a pasta shop and a pizzeria. Nearby, St. Peter’s Church is host to an Italian street festival.

One of Amato’s early customers was Peter Buck, who grew up on a nearby farm eating Italian sandwiches before moving to Connecticut, where he helped the founder of the Subway chain open his first restaurant.

Buck, who’s now in his 70s, told Bowdoin Magazine that he always grabs an Amato’s Italian when he returns to Maine.

“I can get a Subway all over the country but I can only get Amato’s up there,” he said.